The CETME is the predecessor to the G3. It was designed first, by the same team.
Problem is, it tends to jam in sandy conditions in the field. Both the CETME and the G3 destroy the brass they are fed (forget about reloads, the fluted chamber ends any thought of that) and they tend to be very nose heavy. Also, most US CETMEs were Frankenrifles put together by Century Arms, and we all know they weren’t the best to do such a job... Headspace problems are common, sadly.
The fluted chamber does not damage the brass in any way.
Headspace is not an issue.
Bolt gap is, and it is easy to check.
Its also easy to rectify.