Please verify that the tag changes are really not written to the files:
1. Change some tags.
2. Check the actual file tags in Action Window > Tag > Format (Click the first line in AW > Tag to open the "detailed format info" window. It shows the exact tags directly from the physical disk file)
If the format info shows old unchanged tags then we can continue and try to resolve the problem (sample files may be needed). If the file format appears to be fine, it can be a write permission problem (caused by OS level user rights, antivirus program, etc). If it appears to be a rare, previously undiscovered, bug in MC13 JRiver may choose to fix it only in MC14.