Sessions resetting when ECMP is active

[pavjke]

Hello, I've the OPNsense setup with two L3 uplinks through switching fabric. Routing  in this setup organized via BGP. No static routes. Additionaly I configured ECMP for load balancing and effective use of uplinks bandwith. When OPNsens work with one active link (another is switched off or I set up an as-path prepend, etc) everything is OK. But when both uplinks is active I've faced the problem with random break sessions. In traffic dump I see that session (SYN) initialize through one way, let's call this way "A", OPNsense receive (SYN ACK) from same way, but next messages periodically can be sending through another way, let's call this way "B", which lead to session disconnection (RST packet arriving). Where in settings I can check which hash policy and load balancing algortym (per-packet/per-flow) is OPNsense uses? I think this is the problem or am I wrong?

I've using the OPNsense 22.1.4_1-amd64 version.