MS Project Master file won’t allow Duration/Deadline edits

I’m troubleshooting an unusual issue with a long-standing Microsoft Project Master/consolidated file containing multiple linked subprojects.

After replacing one subproject with its latest monthly version, certain fields within that subproject cannot be edited from the Master file. Specifically, I cannot edit fields such as Duration or Deadline, while other fields, such as Text and Baseline fields, can still be edited normally from the Master. I’m sensing the theme has to do with fields that require calculation.

More context:

• This issue arrived after we migrated MPP files from a cloud server to an on-prem server.
• Previous month’s Cloud server MPP file works fine in the Consolidated environment
• The master file creates the issue when I replace the cloud-based MPP with the current month on-prem version.

Troubleshooting completed:

• The subproject works normally when opened directly.
• I created a brand-new blank MPP to use as the Master file and inserted the exact same subproject. Duration and Deadline are editable through the new Master.
• In the new consolidated file and repeated the normal download from on-prem/replacement process. Everything works correctly.
• The problem therefore appears to follow the existing Master MPP, rather than the subproject.
• F9/recalculation does not resolve the issue.

The existing Master has been used for a long time and contains multiple inserted/linked subprojects and external relationships.

Important constraint: I want to avoid rebuilding the Master or use a repair method that regenerates existing task UIDs. A higher-level consolidated schedule relies on the existing UIDs.