I have found that on my RPi 4 4GB even though I have the memory cache set to 3GB it is only using 768MB. In .001 I had it set to 0 so that it would cache to the internal storage and that worked properly...except for the fact that reading/writing to the MicroSD card resulted in video stuttering but the cache setting were being followed. Is this a known issue?
Also, how big of a donation would be required to get HBR audio moved up the queue? LOL