Proton: 1765195901 experimental-10.0-20251208 - regression 1 seems to be fixed, no audible sample cuts (fingers crossed for no further regressions on this).
Proton: 1762451175 experimental-10.0-20251106b - regression #1 is back to the "all the speech samples are played not upto the very end" state (but not completely muted like it was in 1761241153 experimental-10.0-20251023...
Note: 1757428112 proton-10.0-2e to 1731348819 proton-7.0-6f means the ones available in the official SteamOS right now, it doesn't mean I've checked all the minor builds between them.