Every GBBR gun will fail eventually, some are design flaw, others are material problem
Take WA system for example, its both design flaw (evidence shown in RA-Tech and Inokatsu failure) as well as material (AGM, Well, King Arms, VFC, G&P WOC-x...)
KJW designed better so parts are less likely to break, the material is the problem. Though the pressure on those are no where high stress as WA
WE material seem to be the main issue, their continual use of pot metal has cause a lot of parts to fail prematurely, and those made of steel are low quality so they break easily
If you add classic to the list (External Air GBBR) it purely depends on who made it, If it's Escort, make sure you upgrade the brass part to Stainless steel as very long run (20k+ or overclocking the gun) you will have problem.
I know daytonagun uses sacrifical parts, you just need to replace those parts every 10k or so. (Those parts are screws which are notoriously cheap but quite durable, typically purchasable in the $5-10/100 pieces)
I can't commet on SRC, but the new GHK's gun seems to be pretty positive review from the Taiwanese player (GHK PDW & AKM, the 5.45 AK series are piece of junk)