I have 2 ISPs, 1st one is connecting via pppoe, default route marked. This is DAS route.
2nd one has static setings, IP address, network, gw with public IP(/29 network). This is AS route, marking as O2.
I have some mangle rules, half clients goint via ISP1, another via ISP2.
This setup working properly.

Issue.
When isp1(pppoe) is down a I have these troubles.
I`m not able to connect to gw from internet (winbox), I`m not able to ping gw (I can ping isp2 gw only)...it seems like all packets stopped in ISP2 gw.
DNS of MT stoped working too (allow remote request is marked).
I`m not able to traceroute or ping any internet site from my gw (CCR1009) via hostname or ip addres, but i`m able to do it if I choose routing table O2. But There is only one default route O2, because pppoe default route is missing (because dynamic). I think this route have to be main in this case.
I have to mangle all packets as O2 (why, there is only 1 default gw) and clients must requesting directly google dns, not GW DNS (there is google dns too) if I want to go to the internet.

Why dns, remote access are working properly via ISP2 if ISP1 is up, but not working if it is down?

My theory about this bug.
I can see 3 routing table in traceroute e.g. Main, Radiolan(ISP1) and O2. I can use all these 3 routing table in traceroute and all working properly.
But when ISP1 is down and I try use main or Radiolan there are no results, I can use only O2.
And this is the bug I think....Mikrotik is holding ISP1 as main routing table and ignoring its offline status. Mikrotik DNS trying use main routing table but ISP1 is down so didn`t respond to client.
Winbox or icmp packet incoming from internet is trying to send answer via main routing table but ISP1 is down so I`m not able to ping or connect with gw from internet.

/export file=anynameyouwish (minus router serial number, any public WANIP information, keys etc.)