Switch vs Bridge config

I am looking for a real explanation on why this behavior happened.

Have several 450’s deployed. Have just been creating a bridge and bridging the ports together. Mainoy due to familiarity, and no “switch” open in winbox. This setup has worked fine up until today. Installed a new 450 plugged into a 2011 because we needed more ports at a small grain leg. 450 would not pass traffic to the 2011. Would show up in IP neighbors, but could not even mac-telnet to it.

After troubleshooting, we added all the 450 ports to the switch chip.
/interface ethernet switch set switch1 switch-all-ports=yes

/interface ethernet
set [ find default-name=ether2 ] master-port=ether1
set [ find default-name=ether3 ] master-port=ether1
set [ find default-name=ether4 ] master-port=ether1
set [ find default-name=ether5 ] master-port=ether1

I understand the switch chip is better, and it’s switching and not bridging. I just am looking for an explanation to why this happened all of a sudden. We have several cookie-cutter sites where this is not an issue. As a result, it’s hard for the client to see why it has been working all this time and all of sudden going to the switch chip solved this issue.

Maybe spanning tree protocol problem…
Try disable (r)stp .
I have many problems with this. Mikrotik products have not been very good with L2 protocols.
But this can cause other problems depending on your infrastructure. So be careful.