I have this annoying issue where solid infill on the bottom layers doesn't print properly. It also affects walls on those layers. It looks like under extrusion to me, but it doesn't make sense.

• It only affects solid infill bottom layers (I.e. layer 2 and 3 for my regular slicer settings)
• it does not happen on first layer.
• it's not a clog issue, rinsing and cold-pulling doesn't fix it. Brand new nozzle + hotend didn't fix it either
• it's not a flow capacity issue, it happens even with flow as low as 2mm3/s. I've used both Stefan's weighing method and orcaslicers built-in flow calibration and they agree it tops out around 25mm3/s and slicer is conservatively set to 20mm3/max
• it's not speed related, it happens regardless of speed, from 10mm/s to the regular 200mm/s
• internal solid infill line width is set to 105%, same as top layer.

Is there a slicer setting I messed up? Prints turn out ok, slight indent only on layer 2 and 3 because of this. But this just bugs the hell out of me because it shouldn't be happening.

Edit: it's a Qidi xmax-3 printer