I think (although I have no prove yet) the reason is that CardDavMate sends all images in PNG format.
- This makes images (especially photos) really big, and there are IPC-induced size limitations in what DAVdroid can put into the PHOTO blob.
- It seems like BitmapFactory which is used to inflate the image can’t process this specific image, or images from CardDavMate, or PNG images in general.
If my assumption is true, then this is an incompatibility between CardDavMate (sending PNG images) and Android (not be able to process these PNG images). The VCard 3 RFC doesn’t say anything about which image formats have to be supported.
Do you know why CardDavMate sends photos as a PNG? Although it’s of course a valid choice, JPEG makes much more sense in my opinion (takes far less space, especially for photos). For logos, PNG may be a a better choice.