After un UPgrade to 6.4.6 it didn't get an better. In fact it got worse.
After the upgrade (which threw no errors) sd-wan seemd not to work properly anymore.
The same settings and rules that worked well in 6.2 now caused internet to slow down and downloads to get stuck and ssh tunnels to rapidly disconnect.
I finally broght sd-wan back to normal behaviour when I deactivated all sd-wan rules so only the implicit default loadbalancing rule is still active. This renders the loadbalancer rather useless and makes the fallback I wanted impossible...
I also opened annother ticket with TAC on this.
"It is a mistake to think you can solve any major problems just with potatoes." - Douglas Adams