gRPC FieldMask not rendered correctly in Swagger Page

[ricknbaker]

What version of gRPC and what language are you using?

Microsoft.AspNetCore.Grpc.Swagger v 0.8.11
C#

What operating system (Linux, Windows,...) and version?

Windows 10

What runtime / compiler are you using (e.g. .NET Core SDK version dotnet --info)

MSVC 17.9.6 / net 8.04

What did you do?

Updated Microsoft.AspNetCore.Grpc.Swagger from 0.3.4 to 0.8.11

What did you expect to see?

Swagger page allowing me to add repeated paths to a fieldmask.
Rendering an 'Add String Value' button and a removal option:

What did you see instead?

Swagger page allowing only one path.

The option to 'Add String Value' has gone:

Example .proto:

// The request message 
message EntityRequest {
  string EntityTypeCode = 1;  
  string SearchCriteria = 2;     
  bool ActiveOnly = 3;
  google.protobuf.FieldMask mask = 4;
  bool ExplicitPathing = 5;    
}

If I create my own FieldMask type, it all starts to work again:

message FieldMask2 {
    repeated string paths = 1;
}

...
 bool ActiveOnly = 3;
  FieldMask2 mask = 4;
  bool ExplicitPathing = 5;    
...

Any idea why it doesn't like the regular FieldMask?