OPNsense PPTP connection fails after 2min

So i have recently installed OPNsense on my home router. It used to run XenServer with a file host vm and a pfsense vm, it was mostly fine but it took too long to boot and had some rare but annoying problems. So i wiped it all and installed OPNsense on bare metal.

The way my ISP works is that i get my public ip and connect to the internet by establishing a PPTP connection. So i configured my static local ip and the pptp connection, and everything seemed fine… up until monday when i had to work remotely via rdp. The connection failed every couple minutes and when i checked the logs (recent log but same deal):
|2020-06-17T11:44:01|ppp: [opt2_link0] PPTP call terminated|
|2020-06-17T11:42:03|ppp: [opt2] IFACE: Rename interface ng0 to pptp0|
So i called my ISP and they said they would get back to me. And after an hour everything was normal. But around 20:00-21:00 it started again. The next day same deal in the morning, but this time i get a call from my ISP telling me they have no idea what the problem is, my router just drops the connection. I looked at the firewall logs and right around when the connection fails, the firewall blocks incoming packets from the pptp server. So either the server sent them thinking the connection was still open when my router closed it, or the firewall blocked those packets and that closed the connection… so i tried allowing incoming traffic from the pptp server and it didnt help. What can be the problem? everything worked fine on both pfsense and a windows laptop…

Okay so i’ve disabled state tracking on the firewall rule mentioned above and it seems to work now. That means that the firewall suddenly decides that the connection is closed and starts to block packets… strange… It’s working fine with this workaround, but could there be a better solution?