I was recently copying some ISO's to USB drive via command line. The copy operation never completed once the file was fully copied. Not sure exactly why, but interrupting it, did cause corruption of the file. Despite the copied file size matching the original.
I mounted the same USB drive directly as root bypassing udisks. The copy operation completed as expected. This clearly seems to be some issue with either how udisks is mounted the drive and/or the mount options.
Mounted via udisks
/dev/sdf1 on /run/media/wlt/4849-D2E7 type vfat (rw,nosuid,nodev,relatime,uid=10001,gid=100,fmask=0022,dmask=0022,codepage=437,iocharset=iso8859-1,shortname=mixed,showexec,utf8,flush,errors=remount-ro,uhelper=udisks2)
Mounted as root
/dev/sdf1 on /mnt/floppy type vfat (rw,relatime,fmask=0022,dmask=0022,codepage=437,iocharset=iso8859-1,shortname=mixed,errors=remount-ro)
Not sure versions of other stuff matter. Since when not mounted under udisks. There were no problems with copy operations not completing. The copied files were copied entirely without corruption and job completed.