Question: Disable or replace mortise locks?

[Brooke Tomasetti]

One of my units has mortise/skeleton key locks/knobs on the bedrooms. We don't have the keys to these old locks, and my tenants say that the doors have locked before, which is a concern (for obvious reasons!). 

I'd like to get these replaced, but I'm worried the only way to do that is to cut the door and put a new block in the door with a regular knob. Is there an easier way to do this? 

The knobs are fine, but I don't want the mortise lock to be able to lock. Any way to disable it? Video here for reference: https://drive.google.com/folderview?id=1PbRX5yHwxf...