I have found PETG to reward going slow. But there are big differences between types and brands.
BBL PETG Basic for example gets a speed limit of 80mm/s from me.
But infill only problems are rare. Usually, overhangs and sharp corners are where I am seeing problems first.
Are you using combine infill? Or do you have vastly different speed settings between outer/inner wall speeds and infill? If the former, definitely disable that. If the latter, curb infill speed to the fastest wall lines (if they print OK).
BW, 
& 
,
Eno