Product and version
FileMaker Pro 13->16.0.1 (and probably earlier)
OS and version
OS X 10.11 and Windows 10 (probably irrelevant)
iMac 27'' Retina 5K late 2014
Although it does not seem to be documented, if Validation Rules are defined for a Global Field, these validations are proceeded just before exiting the field and not just before the Record Commit. However, if an incorrect value was entered by a user whereas a Revert Record[No dialog] step is invoked by a script, this last step is failing with returning an error 1 (operation canceled by user).
How to replicate
Open the attached database
Push the "Test" button
In your script, it is possible to test if the error 1 is occurring and if so, adding a Undo step before another Revert step. this will enter the prior value in the field (which *must* be correct) and then the Revert step will just do its job.