This article explains an issue where the file transfer via MS TEAMS application does not work after configuring unified policy for MS TEAMS application.
If you configure a unified policy on SRX and allow junos:MS-TEAMS application in the dynamic applications knob, users will not be able to share the files via MS TEAMS, as the file upload fails during the process.
This is an expected behaviour, as the MS TEAMS application uses MS Office 365 applications in the backend for the file transfer function.
You need to add "junos:office365-apps" application group as well along with the junos:MS-TEAMS application, in the unified policy for the file transfer feature to work.
TechPub: Application Signatures