[2022] Mouse lag with low fps

My PC is rather old, so I usually lock fps to 30. The mouse cursor is smooth even with low fps though, no lag whatsoever, until I either enter turn-based mod or click on an ability that requires targeting (i.e. Charge), in this case it becomes slow and laggy.

I mean, why is it becoming laggy only in certain situations? The rest of the game runs in 30 fps in any situation, but the mouse decides to behave this way only in turn-based combat. Is there a solution?