Dear developers!
I'm found case of wrong traffic flow:

If packet (tcp/udp) send from one interface of router to another and it will be SRC-NAT
router wait for answer from destination host. But if in this moment disable (or plug off cord) of local interface - all packets belong to SRC-NAT income to out interface proceed router and will be return to default gateway, becase source interface inaccessable at the moment. Out of router packets have souce and destination address reversed.

Reproduce in bridge combination and PHY interface.
While block this traffic with firewall filter

/ip firewall filter add action=drop chain=forward in-interface="OUT-INTERFACE" out-interface="OUT-INTERFACE"

but only if bridge ip firewall is disable. If bridge ip firewall enable - i'm unable to see this packet's flow in any chain

p.s. affected version and board
RouterOS 6.29.1 / SXT 5Lite / x86