ultimaker cura – Weird infill edge problem

I’m having this weird issue; for some weird reason, the infill pattern starts separating from the walls and over time, the print becomes a mess. As it separates, it starts to curve, and you get this curved end rather than a pointing edge that touches the wall.

Strangely, for the first 4-5 mm of print (which is a lot of layers), the print goes all OK. Not sure what is the issue here, hardware, temperature settings or something else?

I’m using a Prusa I3 MK3S+ with Cura as slicer and printed it on 210/60 °C hot end/bed temperature with 0.6 mm nozzle (I’m using a 0.4 mm layer height with adjustable layer height, but that didn’t kick in yet, the print is a very simple box). The filament is eSun PLA+.