Dynamics Community Forum Thread Details

We recently upgraded from Dynamics 365 CRM 8.2 to 9.1 (on-premises), and now we're seeing a strange issue with the Email entity.

Issue Description
When I create a new email, save & close, and then try to:
Create another new email, or open an existing email (from grid or command bar), i get a JavaScript error and the form fails to load:

Une erreur s'est produite. Vérifiez les détails techniques pour en savoir plus.

Détails techniques
ID de session: ***
ID d'activité: ***
Horodatage: ***

Cannot read properties of undefined (reading 'Resources')

TypeError: Cannot read properties of undefined (reading 'Resources')
at Object.execute (***uclient/scripts/dashboardpage.js?v=***:474:182)
at w._executeSyncAction (***uclient/scripts/app.js?v=***:723:692)
at w._executeSync (***uclient/scripts/app.js?v=***:723:419)
at w.executeAction (***uclient/scripts/app.js?v=***:723:201)
at t.dispatch (***uclient/scripts/app.js?v=***:723:5538)
at Object.dispatch (***uclient/scripts/app.js?v=***:1379:1525)
at Object.dispatch (***uclient/scripts/app.js?v=***:723:5027)
at dispatch (***uclient/scripts/app.js?v=***:723:1235)
at ***uclient/scripts/editformpage.js?v=***:470:2503
at ***uclient/scripts/editformpage.js?v=***:470:2541

The URL in the address bar is correct, but the page doesn’t render.
If I press F5 (refresh), the same URL loads perfectly — no cache clearing needed.
What I’ve Already Tried