Hmmm, now I switched on my NAS, went to Sources, then clicked on edit and save in order ot get it mounted. Similar like I did it 100 times. Normally this initiates an update, which in regard to that nothing has changed doesn’t take much time. But now a rescan is going on 
What is weird is that even the USB that has been mounted already is (unnecessarily) rescanned.
I tested with new 3.616. The problem is same. There is on difference. The size of connected NAS shows 15.85TB but my NAS has 6.5TB.
I’ll wait next version. T_T
Right, but with V3.611 it all looked fine (at least in case of my 2 RPIs)
Downloaded the new version 3.616. Again the size indication of the connected drive is incorrect,
the fix for that problem is still pending
Just upgraded to the new release on my 2 RPi4s and the drive size is wrong on both. My Samba drive has about 220 GB available out of 500. It now says 15.85 TB. The figure was correct on the previous version.
Edit: Version is 3.616. I tried deleting the network drive details and then adding it again. No difference, still shows 15.85 TB.
Edit2: Maybe this can be appended to this topic.
I have just upgraded to v3.616 and both drives on NAS are showing 15.85 TB - somewhat larger than the actual drives!
Mine are also 15.85TB, quite close so i didnt even noticed.
Raspi 4
Test version 3.623 has sorted the reported network drive size problem for me
yes, the fix for the wrong size is in place with the test version 3.623
Fixed for me with V3.623 
Also on 3.625 (test mode)
On system version 3.6.25 (rpi4 2 Gb)my usb devices hard disc and dac failed to recognized.Total disaster
You have installed a test release. There where clear instructions not to do this. Please roll back to the latest stable release.
Thank you
Same for me.
Applied 3.631.
NAS capacity display is fixed but still has mpd trouble.
When I reboot the Rpi, music library of NAS is empty. In that status, re-setting ouput device and click save button (maybe restart mpd) solve the problem. Then music library shows normal and I can play the music in the NAS.
