PPTP hangs at boot [RT-AC66U 378.51] (with workaround!)

[meh]

Every time I boot the router, pptp fails to connect:

Dec  1 01:00:30 ntp: start NTP update
Dec  1 01:00:30 pptp[522]: Plugin pptp.so loaded.
Dec  1 01:00:30 pptp[522]: PPTP plugin version 0.8.5 compiled for pppd-2.4.7, linux-2.6.22.19
Dec  1 01:00:30 dhcp client: bound **** via **** during 14400 seconds.
Dec  1 01:00:30 pptp[524]: pppd 2.4.7 started by admin, uid 0
Mar 11 21:10:09 rc_service: ntp 521:notify_rc restart_upnp
Mar 11 21:10:09 rc_service: ntp 521:notify_rc restart_diskmon
Mar 11 21:10:09 rc_service: waitting "restart_upnp" via ntp ...
Mar 11 21:10:09 miniupnpd[518]: shutting down MiniUPnPd
Mar 11 21:10:09 miniupnpd[534]: HTTP listening on port 52726
Mar 11 21:10:09 miniupnpd[534]: Listening for NAT-PMP/PCP traffic on port 5351
Mar 11 21:10:09 disk monitor: be idle
Mar 11 21:10:10 pptp[524]: Using interface ppp5
Mar 11 21:10:10 pptp[524]: Connect: ppp5 <--> pptp (94.254.51.233)
Mar 11 21:10:10 pptp[524]: System time change detected.

And then nothing happens.. VPN status page is showing a red "error!"

However if I restart the PPTP client by disabling/enabling at Advanced_VPNClient_Content.asp

Mar 11 21:22:48 rc_service: httpd 394:notify_rc restart_vpncall
Mar 11 21:22:48 pptp[524]: Hangup (SIGHUP)
Mar 11 21:22:48 pptp[524]: Terminating on signal 15
Mar 11 21:22:48 pptp[524]: Connection terminated.
Mar 11 21:22:48 pptp[524]: Exit.
Mar 11 21:22:49 pptp[609]: Plugin pptp.so loaded.
Mar 11 21:22:49 pptp[609]: PPTP plugin version 0.8.5 compiled for pppd-2.4.7, linux-2.6.22.19
Mar 11 21:22:49 pptp[610]: pppd 2.4.7 started by admin, uid 0
Mar 11 21:22:50 pptp[610]: Using interface ppp5
Mar 11 21:22:50 pptp[610]: Connect: ppp5 <--> pptp (176.10.248.231)
Mar 11 21:22:52 rc_service: httpd 394:notify_rc restart_vpncall
Mar 11 21:22:52 pptp[610]: Hangup (SIGHUP)
Mar 11 21:22:52 pptp[610]: Connection terminated.
Mar 11 21:22:52 pptp[610]: Terminating on signal 15
Mar 11 21:22:52 pptp[610]: Exit.
Mar 11 21:22:52 pptp[651]: Plugin pptp.so loaded.
Mar 11 21:22:52 pptp[651]: PPTP plugin version 0.8.5 compiled for pppd-2.4.7, linux-2.6.22.19
Mar 11 21:22:52 pptp[652]: pppd 2.4.7 started by admin, uid 0
Mar 11 21:22:53 pptp[652]: Using interface ppp5
Mar 11 21:22:53 pptp[652]: Connect: ppp5 <--> pptp (176.10.248.231)
Mar 11 21:22:56 pptp[652]: CHAP authentication succeeded
Mar 11 21:22:56 pptp[652]: local  IP address 10.248.0.48
Mar 11 21:22:56 pptp[652]: remote IP address 10.248.0.1
Mar 11 21:22:56 pptp[652]: primary   DNS address 213.80.101.3
Mar 11 21:22:56 pptp[652]: secondary DNS address 213.80.98.2

It connects just fine. From the first log it looks like there's a race condition with ntp that triggers if time is updated while pptp is connecting, which for me seem to happen at every boot.

I tried to verify this by setting ntp server to 127.0.0.1 to make the time update stall:

Dec  1 01:00:30 ntp: start NTP update
Dec  1 01:00:30 pptp[522]: Plugin pptp.so loaded.
Dec  1 01:00:30 pptp[522]: PPTP plugin version 0.8.5 compiled for pppd-2.4.7, linux-2.6.22.19
Dec  1 01:00:30 dhcp client: bound **** via 8**** during 14400 seconds.
Dec  1 01:00:30 pptp[524]: pppd 2.4.7 started by admin, uid 0
Dec  1 01:00:31 pptp[524]: Using interface ppp5
Dec  1 01:00:31 pptp[524]: Connect: ppp5 <--> pptp (176.10.248.233)
Dec  1 01:00:34 pptp[524]: CHAP authentication succeeded
Dec  1 01:00:34 pptp[524]: local  IP address 10.248.0.57
Dec  1 01:00:34 pptp[524]: remote IP address 10.248.0.1
Dec  1 01:00:34 pptp[524]: primary   DNS address 213.80.101.3
Dec  1 01:00:34 pptp[524]: secondary DNS address 213.80.98.2

And it worked! But now I have time synchronization so I'd be super happy if Merlin could find a way to leviate this issue. Thanks!