The shady programmers want you to spend or suffer.
I know, and I will call out all their cheats that the programmers allow to happen. SP dropping is shady, but by them not fixing it, since it sounds like it's been a thing way before I started playing, they want it to happen. That is why I call it legal cheats. They will probably respond to say that it isn't cheats or they don't like cheats, or whatever they make up. But since it's happening forever, they do like it. We just need to warn new users so they won't spend anything here.
I was even watching a video from one of their content creators on youtube, and they even said, if you don't pay, you have no chance of winning needed credits or a-coins to level up. "How to get A-Coins for FREE in Mech Arena! (F2P Guide)"
This is my bracket for the current tourney. I have no chance of getting first. The person in first has a 30k inventory, second place has 26k. I have no chance. I would have to spends quite a bit a-coin to just get into the top 6. This is crazy. I did black out anything I think would lead to me because I don't want others trying to get revenege on me for calling them out. Not sure if that helps, but we will see.