Frame drops with inventory open.

[Willoguns]

I'm getting significant performance issues / frame drops with my inventory open when it's even just around 50% full. The problems are even further exaggerated with a full inventory.
The issues are incredibly inconsistent - and even just standing still and opening / closing the inventory periodically leads to incredibly hit-and-miss results

My setup:
i7-9700K 5.00GHz (overclocked)
AMD 6800xt
32 GB 3200MHz RAM
game is installed on a very high-quality 1TB SSD

Not long ago I had a 2060 Super and did not have any performance problems at all - is it possible the drops are due to a driver issue?

Edit: my main monitor has a refresh rate of 165hz, is it possible that either this or AMD freesync premium could be causing issues?

[Willoguns]

I've just gone to my config and set force-opengl to false, and this seems to have fixed the issue.
For anyone else having similar (unexplained) performance problems, that should probably be the first thing you check.