There is more on Andriskos in Livy and Diodoros
40a Once again a popular uprising, due to the disaffection of the masses, threatened Demetrius with the loss of his throne. One of his mercenary troops, a man named Andriscus, bore a close resemblance to Philip, the son of Perseus, both in appearance and stature, and while at first it was only in jest and derision that his friends called him "son of Perseus," soon the statement won popular credence. Andriscus, boldly taking his cue from this talk, not only declared that he was indeed the son of Perseus, but adducing a fictitious story of his birth and upbringing, even approached Demetrius with a crowd of followers and called upon him to restore him to Macedonia and to the throne of his fathers. Now Demetrius at first regarded him as a crank. But when the populace had gathered, and many speakers declared that Demetrius should either restore Andriscus or, if he could not or would not play the king, should abdicate,55 Demetrius, fearing the quick temper of the mob, had Andriscus arrested during the night and sent him off straightway to Rome with a full report to the senate of the claims made for the man.
9a The pseudo-Philip, after gaining a resounding victory over the Romans,28 shifted to a course of savage cruelty and tyrannical disregard for law. He put many wealthy persons to death, after first throwing out false and slanderous charges against them, and murdered not a few even of his friends. For he was by nature brutal, bloodthirsty, and arrogant in manner, and was, moreover, shot through with greed and every base quality.
9b The false Philip appointed Telestes general. He, however, seduced by the promises of the Romans, revolted and went over with his cavalry to Caecilius. The pseudo-Philip, enraged at his conduct arrested the wife and children of Telestes, and vented his anger on them.
15 1 [Concerning him there is again an account elsewhere.]22 When King Demetrius sent on to Rome the self-styled son of Perseus, a young man named Andriscus, the senate ordered him to live in a certain city of Italy. But after a period he escaped and sailed off to Miletus. 2 During his stay there he invented tales about himself purporting to demonstrate that he was the son of Perseus. He said that while still an infant he had been given to . . . the Cretan p425to rear, and that the Cretan had transmitted to him a sealed tablet, in which Perseus revealed to him the existence of two treasures, one at Amphipolis, lying beneath the highway at a depth of ten fathoms (?), containing one hundred and fifty talents of silver, and the other, of seventy talents, at Thessalonica, in the middle of the exedra of the colonnade, opposite the court. 3 Since his story attracted much attention, it finally reached the ears of the magistrates of Miletus, who arrested him and placed him in prison. Certain envoys happening to visit the city, they referred the matter to them, seeking advice on what should be done. They scoffingly bade the magistrates let the fellow loose to go his own way. 4 He, on receiving his release, set himself in earnest to act out and make a reality of his mummery. By constantly embroidering the story of his royal birth, he gulled many, even the Macedonians themselves. 5 Having as his accomplice a certain harpist named Nicolaüs, a Macedonian by birth, he learned from him that a woman called Callippa, who had been a concubine of King Perseus, was now the wife of Athenaeus of Pergamum. Accordingly he made his way to her, and pouring out his romantic tale of kinship to Perseus procured from her funds for his travels, a regal costume, a diadem, and two slaves suited to his needs. From her he heard, moreover, that Teres, a Thracian chieftain, was married to a daughter of the late King Philip.23 p4276 Encouraged by this support he made for Thrace. On the way he stopped at Byzantium and was received with honour — a display of folly for which the citizens of Byzantium later paid the penalty to Rome. With more and more people flocking to him, he arrived in Thrace at the court of Teres. As a mark of honour Teres presented him with a troop of a hundred soldiers, and placed a diadem on his head. 7 Recommended by him to the other chieftains, Andriscus received from them another hundred men. Proceeding to the court of the Thracian chieftain Barsabas, he prevailed upon him to take part in the expedition and to escort him home to Macedonia, for he was now asserting, on the grounds of inheritance, a legal claim to the Macedonian throne. Defeated in battle by Macedonicus24 this false Philip took refuge in Thrace. . . . Finally he25 gained the upper hand in the cities throughout Macedonia.
Livy Periochae (Summary)
Andriscus, who pretended persistently that he was the son of Perseus, the former king of Macedonia, was sent to Rome.
A certain Andriscus, a man of the lowest kind, pretending to be a son of king Perseus, changed his name into Philip, and secretly fled from the city of Rome, to which king Demetrius of Syria had sent him, precisely because of this lie; many people were attracted by his false story (as if it were true), he gathered an army and occupied all of Macedonia, whether the people wanted it or not.
He told the following story: born as the son of king Perseus and a courtesan, he had been handed over for education to a certain Cretan, so that, in this situation of war against the Romans, some scion of the royal stock would survive. Without knowledge of his family and believing that the man who taught him was his father, he had been educated at Adramyttion until he was twelve years old. When this man fell ill and was close to the end of his life, he finally told Andriscus about his origin and gave his "mother" a writing that had been sealed by king Perseus, which she should give the boy when he reached maturity, and the teacher added that everything had to be kept secret until that moment. When he reached maturity, Andriscus received the writing, from which he learned that his father had left him two treasures. Until then he had only known that he was a foster son and had been unaware about his real ancestry; now his foster mother told him about his lineage and begged him to avoid being assassinated by departing from the country before the news reached [king] Eumenes [II Soter of Pergamon], an enemy of Perseus. Frightened and hoping to obtain assistance from Demetrius, he went to Syria, where he had declared for the first time who he was.
Thessaly, which the false Philip wanted to invade and occupy with his armies, was defended by Roman envoys and Achaean allies
 After the false Philip had massacred praetor Publius Juventius with his army in Macedonia, he was defeated and captured by Quintus Caecilius, and Macedonia was subdued again.
It does not seem to me that this pretender levied a Macedonian style army, rather he would seem to have a Thracian style force based on cavalry and theurophoroi. That Publius Juventus' army slipped away in the night speaks more of an ambush than a pitched battle to me. nor is it entirely clear that the army he was commanding was based on a legion, the Oxyrhynchus Epitome of Livy has (Book L, ll108-9)
Per socios popu[li R. Andriscus ex Thessalia pulsus]
in ultimam T[hraciam.
'By the Allies of the Roman people Andriscus was driven from Thessaly to the ends of Thrace.' and later the bald statement ll 126-7
in] Thessalia exercitus caesus.
[Andriscus a] Metello captus.
'In Thessally an army was lost. Andriscus was captured by Metellus'
Hope this is of help, but IMHO not a phalanx victory.
When you think about, it free-choice is the only possible option.