Yeah it happened to me, that's why I hate assist achievements. I had a situation where I did get an assist icon, but it didn't count towards the "collaborator"

So I got 3 assists which was clearly visible when I opened stats with tab button, but at the end of the battle I didn't get a collaborator reward. 

Also I noticed that if I only damage mods I don't get assist at all so maybe that is your case 

Thanks! The issue might indeed be mods related since now all bots have mods, too ( they didn't earlier at my level). 

The possibility occurred to me but I was hoping it's not the case. It indeed makes earning assists unnecessarily difficult.

"but at the end of the battle I didn't get a collaborator reward."

Unless there's a bug, this could be for a couple of reasons:

1. The assists weren't by a single mech.

2. The assists were in different rounds of a match.

I forgot to mention, I did keep that in mind, wrote down assists I had with one mech in 1 round and didn't shoot in 2nd. (Didn't die in the 1st and hid in the 2nd round so I can test this) because I suspected this had happened before, and I was right. It was definitely a bug