Multi WAN - timeouts

[amather]

Hello!

I've successfully set up Multi WAN, but still cannot use it as clients on the LAN run into timeouts:

*) WAN - Provider1 with 192.168.8.99/24, gw: 192.168.8.1 - DNS and monitoring IP: 8.8.8.8
*) OPT1 - Provider2 with 192.168.9.99/24, gw: 192.168.9.1 - DNS and monitoring IP: 8.8.4.4

Both GWs in Tier1, sticky connections enabled with no "Source tracking timeout" configured. Clients use 1.1.1.1 and 9.9.9.9 as DNS Servers. FW rule on LAN interface added with "LAN net" as source and "InternetGroup" (name of GW group) as Gateway.

My current test is to use 2 different clients on LAN and go to speedtest.net. To my understanding, if one client already performs a speed test (i.e. one WAN connection is heavily in use) the other should run its speedtest over the 2nd WAN connection.

This is also what I see (each client is shown on the website as connected from different provider), but rather quickly in the test, either one or both clients start to time out (speed test fails). A reload of the page also times out on host name resolution. Command line test confirms that DNS requests time out. As do any other requests (i.e. ping on Internet-IP addresses). So basically no internet works at all.

After a while (feels like 30sec to max. 1 min) the clients can connect again, but soon (even without running speedtests) this timeout problem reappears...

I run OPNsense 19.7.2-amd64


Did someone else experience similar problems or did I miss something in the confiruation or in my understanding how this should work?
 
Any help is highly appreciated, thanks!