Error: This action cannot be completed because the other application is busy

[TMProjection]

i have this issue aswell
but mine is caused due to .psd .psb files
using FastPictureViewer Codec
once it is installed, and i go into a folder with those files, when xyplorer starts to generate those thumbnails, i get this error and i need to close xyplorer.exe from task manager

[admin]

i have this issue aswell
but mine is caused due to .psd .psb files
using FastPictureViewer Codec
once it is installed, and i go into a folder with those files, when xyplorer starts to generate those thumbnails, i get this error and i need to close xyplorer.exe from task manager

1) Did you already try PreviewEarlyFactory=2?

2) This message does not come by itself but usually when you trigger something else with mouse or keyboard while thumbnails are being generated. True?

3) Once I've put the responsible call into a background thread this issue will be history.

4) BTW, I recommended FastPictureViewer in the past, but not anymore. Last time I installed it (Nov 2022) it destroyed my taskbar during installation.

[TMProjection]

no i have no idea what
PreviewEarlyFactory=2
does

i spent literally like 2 days this week sorting out my thumbnails system (i was setting up a new desktop system)

so the cause of that error messege came from FastPictureViewer Codec (as mention in post above)
when it generates .psd .psb
and i noticed this happened as soon as i installed FastPictureViewer Codec

to diagnose the issue i made a folder with MANY picture formats
refer to image: https://gyazo.com/3b24277dc316a2618f064f78aab16a21

so to mess around with FastPictureViewer codec i opened its control panel:
C:\ProgramData\Microsoft\Windows\Start Menu\Programs\FastPictureViewer\Codec Pack Control Panel.lnk
uncheck everything except, Sony ARW, SR2, SRF
this just means it will only load embeded thumbnails for Sony files, the rest wont be embeded, but it still loads a thumbnail somehow

im not sure how this was related to .psd .psb but it resolved the issue, and i checked many folders that game me that error when generating and i havent seen it since

BUT TO ANSWER YOUR QUESTION 2
yes the error comes up when i click in xyplorer after it hanging for around a minute whilst the status bar at bottom said generating thumbnail for either psd or psb
have to force shut down xyplorer from task manager
if i run xyplorer again in same folder and leave it to generate thumbnails, it just wont, it hangs, so i think putting that call into background would just hide the issue (or maybe im wrong? im not a developer, just a power user haha)

i have issues with my windows explorer / taskbar too, but these issues i noticed started after setting up O&O ShutUp10, i got a feeling maybe i disabled some necessary windows explorer service or something
(this issue is when i press win + e for example, it hangs for like 30 seconds sometimes and only then launches win explorer, or taskbar just crashes and i have to restart win explorer manually)

[admin]

no i have no idea what
PreviewEarlyFactory=2
does

There are many ways to create thumbnails (IShellItemImageFactory, IExtractImage, GDI, native code), and many factors (file types, Windows version, installed CODECs and thumbnail handlers) that control performance, quality, problems. The situation is almost infinitely complex. It is pointless to expose all of this mess to the user -- it would make him a programmer rather than a user. But there are at least some options available to the user:

Configuration:
- Configuration | Preview | Previewed Formats
- Configuration | Preview | Thumbnails | Show thumbnails for RAW files
- Configuration | Preview | Thumbnails | Show thumbnails for non-images
- Configuration | Preview | Thumbnails | Quality
Tweaks:
- Thumbs64Skip
- Thumbs64Ext
- PreviewEarlyFactory

PreviewEarlyFactory originally controlled the sequence of attempts (which way to try first); in the meantime its function became it bit broader:
0 = [default] try IShellItemImageFactory first for some file types (internally hard-coded after years of experience), on failure fall back to IExtractImage
1 = try IShellItemImageFactory first for all file types, on failure fall back to IExtractImage
2 = try IExtractImage first for all file types, on failure fall back to IShellItemImageFactory
3 = try IExtractImage only for all file types, never try IShellItemImageFactory (added 20230309, not yet documented until now )
4 = [planned], bit OR-ed to the above values, making them 4,5,6,7: run IShellItemImageFactory in separate (64-bit) thread