This idea is related to Migrating the SFMs using the SFM migrator. I came across this issue when i was done with migration and migration went successful. This migration included my "Create Installed Product" from Location. When i tied to create a Installed product from Location and click on Save, the SFM did not save instead, it kept on showing me the message "Processing".
when i investigated the issue, there was field in Source environment(from where I migrated) which was not present in Destination environment(to where i migrated) and the that field was being used for mapping purpose in "Location to Installed Product" field mapping.
Idea here is, whenever a field referred in SFM mappings is not present in destination environment can a error be thrown in SFM migrator while validating. Right now error is thrown for SFM expressions when a field is present and the user migrating the SFMs does not have access to the field but the same does not work for SFM Mappings.