setting it to true seems to fix it
That's likely because your client (Emacs, etc) sends incorrect language ID for those files.
These are the language IDs that should be set for each file type:
ts - typescript
tsx - typescriptreact
Previous version of the server was less strict but that likely caused hard to spot issues at a later point.
If you look at the textDocument/didOpen request then you'll see what languageId is being passed.