Multi WAN Failover -> Traffic does not go back to WAN1

[cc_aero]

Hi all!

first - sorry for my english, i'm German people  :-X

I have pfSense Multi-WAN setup running. This setup is running about 6-7 month without any problems.
WAN1 is a LTE-Connection. The LTE-Modem is directly connected to the pfSense-machine via ethernet. The Modem pass-througt the public IP-Adress directly to pfSense's WAN-Port via DHCP.
WAN2 is a DSL-Connection with PPTP Dial-In.

I have created two Gateway-Groups with Failover-config. Trigger is "high latency or packet lose".
group1: Tier1 = WAN1, Tier2 = WAN2
group2: Tier1 = WAN2, Tier2 = WAN1

Traffic, which requiere high bandwidth (http(s), mail, etc), is routed with a firewall-rule form LAN over group1.
All other Traffic, which requiere low latency, is routed with a firewall-rule form LAN over group2.

Since the upgrade to pfsense 2.3.2 a problem appears:
Example for group1: If WAN1 goes down then all traffic goes over WAN2. But when WAN1 is back online (the Gateway is also marked as online at the dashbord) the traffic does not go back to WAN1.

This happends also when i start a new device after WAN1 goes back online and start a completly new connection to the internet.

The Traffic goes only back to WAN1, if i reload the filter or reset the states.

Also interessting: If i mark the Gateway WAN1 manual as "down" und later back to "up", then the Traffic switch automatic back to WAN1.

Is there a bug in pfSense since version 2.3.2 or is this a "feature" or does i have a bad configuration?

Thank you in advance.

EDIT: The issue remains also in version 2.3.3