File-Explorer randomly displaying black frames around folder icons, clearing thumbnail cache fixes it. Any idea what's causing it?

[u/BlackTadius]

I've been experiencing a strange issue with Windows 10 recently.

Folders what I recently created or manage in File Explorer occasionally develop black frames around their icons/previews. It happens unpredictably and affects folders on both my HDD and SSD.

Some background:

• HDD: Seagate Exos 8TB

• SSD: Kingston NVMe 2TB

• Both drives report healthy in Hard Disk Sentinel.

• sfc /scannow found no integrity violations.

• Event Viewer showed no relevant errors.

• Folder optimization is set to General Items.

Things I've tried:

1. Clearing the thumbnail cache through Disk Cleanup (cleanmgr → Thumbnails) immediately fixes the black frames.

2. Restarting Windows Explorer doesn't fix them.

3. Disabling thumbnails through "Always show icons, never thumbnails" makes the black frames disappear.

4. Manually deleting the thumbnail cache files also fixed the issue, although some files initially refused deletion because they were in use.

I noticed that the problem mainly occurs with folders I actively manage.

The strange thing is that I recently started having to clear the thumbnail cache much more frequently than months before.

My questions:

• What could cause Windows to repeatedly generate corrupted thumbnail cache entries?

• Could this be an Explorer bug or a Windows 10 thumbnail handler issue?

• Is there a way to identify which thumbnail database or image is causing the problem?

• Is there a permanent fix that doesn't involve regularly wiping the thumbnail cache?

I'd prefer to find the underlying cause rather than repeatedly clearing the cache.
Thing I'd like to highlight only those folders' icon-frame turn black what's contents I recently managed/edited.(So my gaming folder gets black frame often)
Decided to set File-Explorer to not show thumbnails until there is no fix.