Hi there,
Well, there could be a limitation in the manager itself. Or something broken in the XFCE installation... even a possible conflit in the XFCE installation Vs Kernel Vs hardware.
Seems this part can have some troubles sometimes since, for example, in Manjaro Linux 16.02 I think , just opening the Wallpaper folder crashed the window.
Maybe some Wise Linux Gurus in these parts can shed some light on this obscure situation.
Cheers!