Trouble with the Upload plug-in MacOS BigSur

Upgraded my dev platform to BigSur. My partner is still working (on the same app) in Catalina. On his system, the Upload plug-in is working. On mine, under BigSur, I’m getting silent failures. The database record saves but no image uploads.

I believe it is not able to upload the image to the tmp folder right from the get go, but I cannot figure out how to trace the behavior.

Anyone have experience with this setup or issue?

I also work with BigSur, but i don’t use any upload plugin.
Fileupload with e.g:

echo $this->Form->control(‘profilepicture_file’, [‘type’ => ‘file’]);

works with no problems.