I've noticed this thing when my character was level 8 or so. When you level up and try to take any talent EXCEPT companion-related (Merciless, Resilient and so on), one of existing talents gets overwritten by new one. If you take four companion-related talents (and only them), however, it's fine. But sooner or later they end, and you're forced to take another one - and, well, inevitably experience this issue.

Here's a screenshot before level up:

 

Notice I have all 4 companion talents, so I can't "workaround" this anymore. Now here's a screenshot after level up.

 

 

Here, I've taken Gunner and, as you can see, Gunner replaced Vicious Companion. I believe this issue affects Sagani as well.

I'm playing on 3.0 beta. On 2.0 this issue persists as well. I'm not using any mods. Renewing cache didn't help either.

Hey Fiery Rain,

 

Thanks for pointing this out to us. I have written up a bug report and added it to our database.

 

Thanks a bunch!

Update: It seems in new beta patch this bug has been fixed (hopefully). Thanks guys and Aarik in particular, keep it up!