450C to 450G restore, strange outcome

Let me start by saying I am a novice in dealing with MikroTik routers. The customer has 7 of these routers in between the computer and network drop, it was really an over reaction by this customer.

They had several of these RB450C fail and I ordered replacements amd was sent the RB450G models.

I mistakenly thought I could use the backup and restore process to simply save the current configuration on a failing 450C running 6.28 and restore on a RB450G running 6.43. I know now that this was the incorrect process and I should have use import/export and check the MAC addresses but here is what happened

When I connected the new 450G into the network it didn’t communicate and when I checked the quick set page, somehow the new router changed its configuration to one of the other 450C configuration. I then tried again to restore the configuration and it happened again.

I then took a 2nd unit that I had programmed at home and connected to a 2nd location and it didn’t work either, I again checked the configuration and it had changed to the 1st room configuration. Minutes later I received a call for another 450C that went down. I went to a different floor and this unit did not communicate, I connected to the webgui amd the quick set page showed that it had the configuration of the 2nd room. I reprogrammed this router while it was disconnected from the network and it worked again. When I made it back upstairs to the 2nd room, it had taken on the configuration of the 3rd room router on the different floor

I know I messed up by incorrectly restoring the new units, but has anyone seen any behavior like this?

Is it possible that when I thought I was restoring the router I was connected to, I may have been actually restoring another one on the network?

What us the best practice when importing a file to the router, using the webgui, winbox, serial?

Thanks for you help with this

It seems to me that you restored the wrong backup to the router, i.e the 2nd floor backup to the 1st floor router (just an example), and the new router got the MAC address of the other one you already have, than, having them in the same broadcast domain (maybe), you are connecting to the wrong router via MAC.