Wyse device not deleting

We have a few wyse devices that haven't checked-in for over 3 months.  We have tried deleting them from WDM 5.7 but no joy, we get error message client can not be deleted due to pending update. I found out that on first deleting the device you don't get that error message.  The error message only comes up when the command to delete is register with WDM in the Real time command section.

I have gone to real time command section and delete the command but still the device is not being deleted. 

If I force delete the device, will the device still check-in or whats the best way to delete a device that just wouldn't delete

What does Force-delete do?