PPTP server stop working properly in the logs I see an WINBIND issue any ideas how to resolve or where to look.

Mar 23 20:04:34 vuurmuur pptpd[20395]: CTRL: Client 192.168.2.254 control connection started
Mar 23 20:04:35 vuurmuur pptpd[20395]: CTRL: Starting call (launching pppd, opening GRE)
Mar 23 20:04:35 vuurmuur pppd[20396]: Plugin winbind.so loaded.
Mar 23 20:04:35 vuurmuur pppd[20396]: WINBIND plugin initialized.
Mar 23 20:04:35 vuurmuur pppd[20396]: pppd 2.4.5 started by root, uid 0
Mar 23 20:04:35 vuurmuur pppd[20396]: Changing interface to pptp0
Mar 23 20:04:35 vuurmuur pppd[20396]: Connect: pptp0 <--> /dev/pts/0
Mar 23 20:04:35 vuurmuur pptpd[20395]: GRE: Bad checksum from pppd.
Mar 23 20:04:35 vuurmuur systemd: Device sys-subsystem-net-devices-ppp0.device appeared twice with different sysfs paths ...
Mar 23 20:04:39 vuurmuur pppd[20396]: Winbind has declined authentication for user!
Mar 23 20:04:39 vuurmuur pppd[20396]: Indicates the SID structure is not valid.
Mar 23 20:04:39 vuurmuur pppd[20396]: Peer lexvroemen failed CHAP authentication
Mar 23 20:04:41 vuurmuur pppd[20396]: Connection terminated.
Mar 23 20:04:41 vuurmuur pppd[20396]: Exit.
Mar 23 20:04:41 vuurmuur pptpd[20395]: GRE: read(fd=6,buffer=7efe6aa3e480,len=8196) from PTY failed: status = -1 error = ...
Mar 23 20:04:41 vuurmuur pptpd[20395]: CTRL: PTY read or GRE write failed (pty,gre)=(6,7)
Mar 23 20:04:41 vuurmuur pptpd[20395]: CTRL: Client 192.168.2.254 control connection finished

For you info IT's double NAT configuration.