Mikrotik strange situation?

Question

Mikrotik

Good evening.
There is a Mikrotik and 10 PCs in the
Bridge network with all the added ports.
12 port is free, without wire.
the network 10.0.5.1/24 is registered on the Bridge in ip->addresses.
and on the 12th port the network 10.0.5.1/24 is registered in ip->addresses.
When this network is disconnected on port 12, the Internet falls off on 2 PCs. These PCs are connected to other Mikrotik ports.
PCs get the address via dhcp.

I changed poppies on network cards, addresses too. reconnected these PCs to other ports, the situation is the same.
Again, port 12 wireless.

Answer 1

Leave the IP only on the bridge, and remove it from the port.

Answer 2

In the Mikrotik console /export, do and look for settings for falling computers (by IP and MAC).
You can disable the IP address of the 12th port, and on computers that have fallen off, do it arp /d *, but obviously "this is ju-ju - not for nothing" ...

Answer 3

It was possible to simulate the situation on a home network. It was necessary to disable the port in the bridge, remove the network on the port, enable the port in the bridge, then restart the network card on the PC.
Apparently the past admins didn’t finish something,