When running, Malware Bytes is know to block Song Surgeon function and even cause it to crash. You can easily test if this is an issue by temporarily disable this program (all of its modules) and then opening SS6 again and open a file and repeated the same steps the previous were a problem. If Song Surgeon now works correctly you have identified Malware Bytes as the problem.
All antivirus programs have a setting called exceptions or
exclusions. These tell the program to ignore files, or folders or
programs. Do a search on google for your antivirus program and find out
how to set this up and EXCLUDE Song Surgeon from being monitored by
Malware Bytes.