Unable to solve a TM "cleaning up" issue

Unable to solve a TM "cleaning up" issue. USB 3.0 ioSafe 3TB drive hangs repeatedly. Reformatted several times. I have 2 other active TM backups. New drive just won't get beyond the cleaning up dialog. Have done all the usual things (disk utility on target drive as well as source)... Could it be a 3.0 issue? No sign of sparsebundle issue... This is second ioSafe drive, as first one had same issue and was replaced...