Screenshot Image Files Only Pasting Into *Some* Applications

For about the past month, I've not been able to reliably paste images from screenshots using the 'Clipboard History Switcher'. I've been using Keyboard Maestro for about 6 months and I'm pretty sure that everything was originally ok and suspect that I've somehow modified the macro or a setting but I can't work out what.

I noticed something more specific today, which I hope will help you to help me! If I take a screenshot I can paste it into TextEdit but I can't paste it into Messages or into Bear. If I use Finder's 'Show Clipboard' there's nothing there. It's just grey. Is this because it's using Keyboard Maestro's clipboard not the macOS clipboard–i.e., irrelevant to my image pasting problem?

I've tried the extra options in the cog menu on the right-hand side of the non-text clipboard item ('Paste Image', 'Set Clipboard to', etc) but that doesn't change anything.

In the 'Clipboard History Switcher' menu, the screenshot appears as 'Non-Text Clipboard LONG HASH-LIKE NAME'. Does that sound right or is this where it's going wrong.

Other clipboard items (e.g., raw text, URLs, etc) do paste normally into Messages and Bear.

Any idea what I've done here!? TIA!

in what app, any app in particular?
Try checking the clipboard contents with this app:

pasteboard viewer

it was recommended by another forum user, maybe CCStone.
Allows you to inspect the clipboard.