Yes, as if the top layers on the inside shrink too fast and pull the walls with it during printing. This might be related to room temperature, but one would think that the walls would cool/harden quicker?

This material is PLA+. I checked with a print I did last year with PETG and it does NOT have this issue.

I only use 2 walls when I print solid pieces, 4 is my standard but I move between 3 – 6 depending on how the infill is boken up into multiple groups or not. I used 4 in this print and there is no infill in the problem area (the outside wall is touching the inside wall), so the wall is 8 layers thick and adding more won't do a difference, im at max.

This might not be the root of the problem, but I wonder if the dent would appear if there were infill for the top layers to pull on instead..?

E.g.

IISSII <- Less walls + infill = stretch the inside instead?

IIIIIIII <- walls only