It is much more typical for an TXV to fail open, but I am sure that it is possible for it to fail closed somehow. As the previous poster indicated, excessive moisture in the system can indeed cause the same or similar symptoms.

The good news is that on the 124 the expansion valve can be changed from under the hood. It is a job that is done in cramped quarters and requires lots of care, but can be done.

If it were in my shop, I think I would recommend just replacing the TXV and when doing so, recover, dry and recycle the refrigerant.

Good luck,