Anyone here agree its a myth that the Roman Legions was a professional Military Force?

You are correct that the behavior of modern professional soldiers and that of Roman soldiers is different as these are different times So when looking at mutiny you need to ask why they happened before saying the fact they happend is proof the Romans were not professionals after the Marius reforms. One of the biggest issues with the late republic is the fact various factions in the government would end up fighting eachother-for example Pompeii vrs Gius Julius Ceaser which resulted in the empire. However I would still call them professionals for their time.