No Audio Wave thumbnails for NAS files

I have several hundred wav files.
On my local SSD drive E I can search for .wav in flat view and in the resulting list I can see the wave form when hoovering. Thats perfect.
On the NAS I made the same flat view listing, I get the wav files,
but the hoovering does not show up the wave form.
Once in a similar searc, I got a note: the drive is not indexed, it may take a longer time.
But the Synology drive is connected as a drive V in the MS Explorer.
So in both cases its a win10 environment.
Thanks, Willy

It may mean the thumbnail is taking too long to generate and being cancelled, or is stuck behind others in the queue which are taking too long or have even stalled the thumbnail-generation threads.

If there are video files in the same folder, a bad or slow video codec could be taking a long time or stalling on them, for example.

Indexing won't be a factor here. That's only used for searching, not thumbnails.

I got some new findings:
dOpus is showing the waveform trom the NAS when there is a risk of duplicating the file:
The 1,76 GB wav was stored in Drive E (SSD on the PC) and Drive V (10GB NAS DS1621xs+).
When I try to copy a second time the file to drive V, then dOpus shows the existing wave form of the wav file in drive V and D.
So its created.
That happens ecven with a small wav of 12,9MB.
My goal is to store a lot of wav and avi files on a big quick 10Gbit NAS and use dOpus for a quick preview to identify emty waveforms.
Thans, Willy

It's probably the things I mentioned in my previous reply.

You mention avi files on the same NAS. Thumbnailers/demuxers/codecs for avi files, in particular, are notoriously unreliable. One of those is probably getting stuck on one of the avi files in the same folder and holding up generation of subsequent thumbnails.

Those components are not part of Opus, although you may be able to improve the situation by configuring the Opus Movie plugin so it doesn't try to generate thumbnails. Opus will then ask Windows to do it (and Windows will talk to them on its behalf), which may work better than when Opus asks for the thumbnails directly. Or it may end up being the same, and require updating/replacing one of the involved components that is parsing the avi files.