Gaps in walls

I'm printing on an Ender 3 Pro with a 0.6 mm nozzle, at 200°C for the nozzle and 60°C for the bed, using PLA filament. For a few weeks, I've been trying to solve a problem with gaps in the walls. When the printer creates these gaps, there is a silent single click sound—something like the sound of frying. It’s definitely different from the sound the extruder makes when it’s skipping due to a clogged filament. I thought it might be caused by wet filament, but it also happens with new filament. Now I’m out of ideas on how to fix this. Can you help me figure it out?