[HELP] Interface flap on RB750 after upgrade

RouterOS General
1

Guys, sorry if I’m posting in wrong subcategory – I post it here because I saw there’s someone got this problem too:
(so sorry I’m on panic state; I’m on my phone connection - need to bring this router up again in 2 hours max)

I’m just updating my quite outdated by 2yr RB750 which have RouterOS 6.6.
I decided to upgrade it to the newest stable build, 6.30.4 - hoping I can make sure the router is rock-stable.
It turns out really bad instead : ALL of the interface are constantly flapping UP and DOWN every 5 seconds.
I thought it was the cable issue - but it’s not
A NIC issue - nope, this occured on Linksys AP, my PC, and Cisco catalyst switches.

How to downgrade the router without any LAN access? Is there’s any emergency method that does not involve RouterOS to push another RouterOS? something which is like Cisco ROMMON or Linksys emergency firmware

Thanks before.

2

All,
My router has been downgraded, using the Port 1 (the only one port that not flapping).

Why, when others tell mikrotik is very decent, reliable, but for me, it’s really troublesome. It’s like taking a roullete when upgrading a router. This is the third time I downgrade my router, from 5 attempt I upgrade it. Only 6.3 and 6.6 is stable, the others (6.9 , 6.13, isnt as stable as 6.6)