We did the same test with version FDM 4.10.18 (previous) and it worked and completed successfully.
Observation: the version of the FDM 126.96.36.199 corrected the problem of the restart column with keyword of the Schema (backup), but also caused the problem of FDM which falls in circles at a certain moment and stops writing in the log when it tries to hide the Schema.
Release : 4.10
Component : Fast Data Masker
Resolved in FDM 188.8.131.52