I've been experiencing pretty significant lag spikes or rubberbanding or something.
It's been occurring since after the 3 gorgon sisters quest.

Any time I open or close a menu, the game freezes for about 3 whole seconds.
As well as when I pick up a piece of an artifact e.g. a Bat Fang. But not when i pick up cash/potions. I also use the auto-pick up hotkey for artifact/potion/cash.
Also when I activate a respawn fountain.
Sometimes if I open a chest, it lags. Not sure what kind of loot though.
When it usually takes less than a second to save, while the lags are happening the saving process takes longer too.

It's not unplayable, but hella annoying and I'm scared I'll eat it some time in the middle of a stutter.

For what it's worth this is my first play through with Ragnarok installed, previous sessions without it were fine.
It is also the first time I'm launching the game via online Gog Galaxy.