This is a user space corruption.
Based on the MCH0601 pointer not set error provided, it is likely that the model's Object Table User Space needs to be rebuilt. To do this perform the following:
1. Ensure no one is using the model
2. YDLTOBJTBL
3. YEDTDTAARA YSNCMDLRFA, change value to N
4. YSNCMDL
5. Edit the model and see if you can Z into the files function/access path now.