Same situation happened with someone I know. His wife's previous sponsor/employer declined to give NOC or release of any kind but agreed to cancel her visa.

He cancelled her visa and she left Qatar, then they applied for a family visit visa, and once she arrived here they changed it to long term family visit and now she is here under his sponsorship. It took about 6 weeks to complete all the formalities from the moment her work visa was cancelled to the moment they got her new residency stamp.

However, in some cases, at the VISA STAMPING STAGE, some people have experienced problems. I guess it depends on the officer present at the time.