Unable to get a Image from Wyse G90 or Wyse G941 boxes or able to image these boxes from WDM 4.8 version getting above error Try 1:Merlin-Process-FAILURE_Upload_Image_failed
Have you configured your WDM server to use WIZARD or MERLIN as main imaging process?
Check Configuration Manager-Preferences-Scheduling.
Use WIZARD and PXE while imaging.