Access Denied error when copying across VPN

[WileEMan]

I have setup a local NAS with a hard drive attached to my router in one location and the same setup at a different location (different ISP and IPs). I have established a VPN between the routers with network shares for both locations. I have setup FFS to sync specific files across the network from one NAS to the other (both directions). The idea was that no matter which location I was visiting, I would have up to date files. When FFS starts, it appears that the lock causes an access error (write) on the local drive. The only way I can recover the ability to write is to reboot the router. I can copy from one location to the other using file explorer (either direction), but FFS fails every time.