Problems to send photos via email from DigiKam 9.0

Since I haven’t seen any responses, and my problem hasn’t been resolved even with DigiKam version 9.0, I’m asking for help again—even if it’s just a small tip. I’d really appreciate it.
Maybe I’m in the wrong place here.
I’ve been managing my photos with DigiKam for several years (both on Windows and, a little later, on Linux). I like to send photos via email (from DigiKam because it automatically reduces the email’s file size to a maximum of, say, 5 MB). This has always worked well so far. Starting with Ubuntu 25.04, the Snap version of DigiKam was included, and it stopped working. So I tried using AppImage, and that worked perfectly until, with digiKam 8.5 and then 8.6, the following error message appeared:
The file file:///tmp/digikam-qrJCrb/.BLEJkt/IMG_1945.jpeg does not exist, so it cannot be attached to the message.
I have no idea what could be causing this or how to fix it.
Where can I find help?
Thanks for any tips.

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