Hi,
We have 3 sites (a,b,c):
A - Primary site - Vigor 2860 - Firmware Version : 3.8.9.8_BT - 192.168.1.1
B - Remote Site (problem site) - Vigor 2862 - Firmware Version: 3.9.4.1_BT - 192.168.3.1
C - Remote Site (working Site) - Vigor 2862 - Firmware Version: : 3.9.0_BT - 192.168.4.1

Site B & C Dial into site A using Lan-Lan VPN. Over the last few days, the connection at site B has stopped working at random intervals.
Relevant logs on site B:

<141>Dec 11 08:05:03 DrayTek: [PPTP][L2L][5:Sedl. New][@REMOVED] pppShutdown
<141>Dec 11 08:05:03 DrayTek: PPTP (VPN-2) ==> Protocol:LCP(c021) TermReq Identifier:0x02 ##
<129>Dec 11 08:05:03 DrayTek: PPP Drop VPN : L2L Dial-out, Profile index = 5, Name = Sedl. New, ifno = 12
<141>Dec 11 08:05:03 DrayTek: PPP Drop VPN : L2L Dial-out, Profile index = 5, Name = Sedl. New, ifno = 12
<141>Dec 11 08:05:03 DrayTek: [L2L][DOWN][PPTP][@5:Sedl. New]
<141>Dec 11 08:05:03 DrayTek: Delete exist flowstate of VPN ifno: 12 ....
<141>Dec 11 08:05:03 DrayTek: [PPTP][@REMOVED] pppShutdown

For some reasons, in this instance the logs didn't generate at site A but here are historical logs from when it previously crashed:

<141>Dec 10 13:34:32 DrayTek: [PPTP][L2L][3:Parsons Ne][@REMOVED] pppShutdown
<181>Dec 10 13:34:32 DrayTek: [DHCP] Vigor DHCP server has recycled an IP [MAC: 00-00-00-00-00-10, IP: 192.168.1.222]
<141>Dec 10 13:34:32 DrayTek: PPTP (VPN-6) ==> Protocol:LCP(c021) TermReq Identifier:0x02 ##
<129>Dec 10 13:34:32 DrayTek: PPP Drop VPN : L2L Dial-in, Profile index = 3, Name = Parsons Ne, ifno = 16
<141>Dec 10 13:34:32 DrayTek: PPP Drop VPN : L2L Dial-in, Profile index = 3, Name = Parsons Ne, ifno = 16
<141>Dec 10 13:34:32 DrayTek: [L2L][DOWN][PPTP][@3:Parsons Ne]
<141>Dec 10 13:34:32 DrayTek: [PPTP][@REMOVED] pppShutdown


Internally, nothing has changed on our network with the exception of us decommissioning a server 2012 domain controller at IP 192.168.1.8. this has been replaced by a new one at 192.168.1.10. No reference to this is made on site B or C config but site A has DHCP relay configured as follows:
Lan > General Set up
network Config:
IP address 192.168.1.1
Subnet mask 255.255.254.0

DHCP Sever config
Enable relay - address: 192.168.1.10

DNS Sever IP address - Blank

Things i've tried:

• enabling bandwidth management on site B

• Enabling Sessions Limit at site B

• Recreating VPN profile for site B on site B and site A router config

• Ensured no drop outs of internet connection on either. All sites are on a leased line and the line is functioning fine

I'm really at a loss now as to where to look. Any suggestions are welcome