When a primary buffer already exists and a second CreateSoundBuffer call requests DSBCAPS_PRIMARYBUFFER, Wine returns the existing buffer but discards the new caller's dwFlags. This prevents the caller from using capabilities it requested. Star Wars Episode I Racer (AppID 808910) creates a primary buffer with DSBCAPS_CTRL3D for in-game audio, then its Smush video engine requests the primary buffer with DSBCAPS_CTRLVOLUME for cutscene audio. GetVolume returns DSERR_CONTROLUNAVAIL and the cutscene audio path silently fails, resulting in no sound during cutscenes. Tested with the game on Proton Experimental by swapping the DLL built from this branch, cutscene audio plays correctly with the fix applied. Wine-Bug: https://bugs.winehq.org/show_bug.cgi?id=41047 -- v3: dsound/tests: test if primary buffer is independent on windos https://gitlab.winehq.org/wine/wine/-/merge_requests/10726