Apple has released an update that fixes some bugs with Gmail. The update fixes the following issues, according to an Apple support article:

  • Fixes an issue that prevents deleting, moving, and archiving messages for users with custom Gmail settings
  • Addresses an issue that may cause unread counts to be inaccurate
  • Includes additional fixes that improve the compatibility and stability of Mail

You can download the update by going to the Mac App Store and navigating to the Updates section, then clicking Update.

Source: Apple Support article