Cave hotspots FFPS drops

[JohnKable]

Yesterday i went fishing because i had an active booster. 
I noticed that going in a cave aiming my fishing spear with an hotspot in my field of view dropped my fps from 60 stable to 30.  Standing in the exact same place but aiming elsewhere jumped my fps back to 60.
It made quite hard to land shots since those 30 fps were pretty laggy aswell and for the first time i also missed a few fishes.
I could replicate that in multiple caves but not in surface hotspots.

i have not tested yet on my other PCs but i ran with gtx960 and i5 skylake cpu. non the best gaming setup but also a setup that doesnt see that kind of performance drops frequently.
Last time i had gone fishing was in one of the very first patches so i cant thell if that is about the very latest patch or not. For sure the couple of times i did fishing before i didnt experience any kind of issue.