Are you using bulkcopy or pathcopy? If so, you have repeating fields there, you need to use ITER and copy blanks to the rest of subfields. If not, then individually copy only the fields that you want.
We skipped from 5.2 to 5.4, but I’ve used this method successfully:
PathCopy @null -> 0(0).PID.00106
Copy 0(0).PID.00106.[0]->0(0).PID.00106.[0]
The pathcopy will null all all components of PID-3 (since it works at the root level of the path), the copy (via your zero-stripping proc) will just move the first element of the first repeat to the target side.