This matches a known class of Exchange remoting/serialization regressions that have appeared in various Exchange 2019 / Exchange SE updates where scripts expecting native Exchange objects instead receive deserialized objects through the remote Exchange runspace. [learn.microsoft.com], [reddit.com]

Recommendation

At this point I would:

1. Restore any edits you made to RedistributeActiveDatabases.ps1.
2. Verify the hash on both Exchange servers.
3. Open a Microsoft support case referencing:
   • Exchange SE build 15.2.2562.17
   • RedistributeActiveDatabases.ps1
   • Deserialized.Microsoft.Exchange.Data.Directory.SystemConfiguration.DatabaseAvailabilityGroup
   • $dag.Servers returned as System.String
4. Use manual database activation moves as needed until Microsoft provides a corrected script.