As long as the barrels and bolts head space are in specification then I think any issue with Maylaisian ammo is the ammo.
Years ago I bought a case of Maylasian ammo for cheap, at the KCR MG shoot. I was talking to a fellow MG 42 shooter, and without any mention of Maylaisian ammo, he told me not to shoot it in the MG42, that it would blow the gun up. Another friend of mine that I trust he knows his stuff, said if it's not NATO ammo (circle and cross on the head stamp) then you can't guarantee it is NATO spec. I thought about what these two gentlemen said and thought "cheap ammo with a bad reputation in an expensive gun, do I want to risk it". I gave that case of ammo away.
Now I know there are some non NATO countries that make fine ammo that will run very good through the MG42; Brazilian military 7.62x51 comes to mind, but Maylaisian is not at the top of my list.
I feel pretty good about the lot of Maylaisiasn that I have, which is almost gone, and wont blow the 42 up, but case separations are a possibility.
I MIGHT buy some more, but 10 to 20 cents a round more buys a lot of peace of mind.