grrr, I don't know what happened but it does work now!
This was the error this morning:
#74 {main}
[2020-09-30 07:58:02] production.ERROR: Unsupported image type. GD driver is only able to decode JPG, PNG, GIF or WebP files. {"userId":1,"email":"admin@cloudron.local","exception":"[object] (Intervention\\Image\\Exception\\NotReadableException(code: 0): Unsupported image type. GD driver is only able to decode JPG, PNG, GIF or WebP files. at /app/code/vendor/intervention/image/src/Intervention/Image/Gd/Decoder.php:59)
[stacktrace]
#0 /app/code/vendor/intervention/image/src/Intervention/Image/AbstractDecoder.php(339): Intervention\\Image\\Gd\\Decoder->initFromPath()
The image is a jpg. Strange to see that the log numbering restarted after this error.