The dlc.rpf is the that contains all the game assets (YTD textures, YTD models, meta files, and scripts) for that specific holiday event.
If you cannot use the verification tool, you must find the file on reputable GTA modding forums. Update X64 Dlcpacks Mpchristmas2017 Dlc.rpf Download
Happy modding, and enjoy the holidays—even if it's July! The dlc