1. temporally changed to a standard 2 column Blogger Minima template, then try to change to the 4 column Minima template. Error message - error code bX-jdokxi
2. I found out that there were a few gadgets (formerly Page Elements) that were not deleted (left behind) when changing to the standard 2 column Blogger Minima template. I removed all gadgets (Page Elements), then only change to the 4 column Minima template I actually wanted. EUREKA. Problem solved. No error message. Template successfully changed to the 4 column Minima template.
Important reminder. Before doing anything to the template, always backup template and backup gadgets (formerly called Page Elements). After successfully changing to a new template, you can use the backup gadgets (Page Elements) to copy-paste back into the new template via the LAYOUT.