PPTP VPN mystics on RT-AC88U

[GektorUA]

I have upgraded ASUS router from RT-N66U to RT-AC88U, firmware same on both devices - Asuswrt-Merlin 380.66_4.
Make absolutely same setup RT-AC88U as on old RT-N66 - there is LAN to LAN PPTP, RT-AC88U (LAN A) as SERVER and another router as Client (LAN B), on RT-N66U all works perfectly, but on new RT-AC88U i have a mysterious situation:
i can connect to shares and RDP on computers from remote LAN B to LAN A network without troubles, but when i try connect from LAN A to any PC with RDP or access to share in LAN B - it cannot access, looks like firewall of router blocking incoming packets! I tracert and ping all PCs in LAN B from LAN A, but cannot access any of them! I can't login in WEB interface of LAN B router (PPTP Client) from LAN A (PPTP Server), but from LAN B i can login to WEB interface of LAN A (RT-AC88U)!

I don't understand, why it so with RT-AC88U, when RT-N66U works perfectly in that situation?

 

[GektorUA]

It's look like a bug in Asus firmware, RT-AC88U sometimes reboot when i try to access Advanced_VPN_PPTP.asp page, or VPN PPTP client connects to router and i try to view logs. In other case router is stable.

Any comments about this?