xiaomi – Mi Mover “can’t play this video” while transferring data

I’m trying to use the Mi Mover app to transfer data between Xiaomi phones. The app version 3.0.2 and the sending phone is RedMi 3S. Though the transfer can be set up fine, when I actually start it, I get repeated pop-up messages saying “Can’t play this video” – even though I’m not transferring any videos (nor images). The transfer begins, but stops at some low percentage of the

Why is this happening and how can I fix it?