This is simply the crux of industrial manufacturing. The quality is already at a quite high level. Of course, shit can happen always (like usual), but bad charges are recognized relatively quickly. Not so easy are component deviations. Some of them are directly recognizeable, some only after some time of usage.
But to reach and ensure 100% for every single component of an end user product it would result in exploding costs, which nobody would / could pay. Therefore you need some tradeoffs.
Most issues are already recognizeable at the beginning. You have money back and warranties to cover such exceptional cases. In my ~5 years of reading the RME forum and supporting other users I can say, that defects are rare.
I bought already a lot of RME devices, up to now I had no single quality issue.
The quite high prices of used RME equipment also speak a clear language, excellent quality of devices and long term driver support otherwise the prices would be significantly lower.
This I can't say for every other electronic product that I bought in the past 30+ years, therefore I am very happy with RME built quality.
X10SRi-F, Win7 Prof, Cubase 9.5, UFX+, Octamic XTC, ADI-2 Pro FS BE/DAC, RayDAT, ARC USB