We have a VPN running between two sites on draytek routers. On one of the networks we have TrueNas box which has recently been migrated to Scale from Core. Since then the other location has been unable to access the SMB shares on the TrueNas box but has access to all other NAS boxes on that network
You may want to look at this post
https://forums.truenas.com/t/smb-authentication-breaking-after-truenas-ft-reboots/39439/1