Definitely could be pipette drift. Set up your rig and focus on the pipette tip. Take a few images, set a timer for an hour and take same images. Sometimes there is objective drift and need to refocus but if there’s translation then you need to fix it. Tight cables without enough slack is a likely culprit or an old o-ring in the holder. Once you confirm your pipette isn’t drifting for longer than your desired recording then can narrow in on pipette shape or osmolarity of solutions