What Might Cause Such Printing Problem, Please Have A Look.
First guess is you are trying to print too fast. Reduce print speeds using the front know to half or even quarter speed. So if that helps.
I'm using Prusa PETG filament profile without modifying anything, plus this issue wasn't visible earlier with my other prints.
I also noticed that this issue happens mainly in the center of the bed, I did measure the bed temp in several points with a laser thermometer, the temp almost even all over the bed.
Did you slow down the print speed to at least half, or more? Especially infill?
These gaps are 100% speed related, and evidence you are printing way too fast for the material and probably under-extruding as well (rectilinear infill has an issue, especially when printing too fast).