Wierd infill travel/pattern - Bambu Studio - A1 Printer

Hello,
I’m currently printing grid plates for my DnD sessions but noticed during the print that the extruder started shaping the grid by layer 4, just to cover it up by layer 6 and then shaping the actual grid by layer 8. (All of this att 100% infill)

This of course slows the process down a bit and I have been struggling to find a solution for this in the slice.

Any Ideas if there is a setting I have missed, or if this is a wierd bug caused by my stl? I’ve doublechecked my CAD and there is no indication of any cavities or multiple solids.




Change of bottom shell layer from 3 to 5 seemed to have done it, but I’m still curious why the slicer went for this pattern.