MariaDB GTID current_pos vs slave_pos
Use current_pos to switchover master. Use slave_pos for a regular replication.

current_pos - last change in GTID domain

slave_pos - last replicated change applied by SQL thread or parallel workers on the replica.

So, imagine your ordinary replica (node2) switched to a master. slave_pos not incrementing, because changes are applied directly without any replication. Then you need to reconfigure cluster and make the new master become replica again.

What you will see on node2?

SHOW global variables like '%pos%'?


you will see, that slave_pos stopped incrementing on the moment of switchover, 
current_pos incrementing correctly.

In order node2 to become replica you must use current_pos, after the workload switched to a new master.

Summarizing:

slave_pos


use this option when you don't pretend to write to the replica
you don't want the transaction id part of the GTID to increment on the slave
you are adding a new slave to the cluster and would like to start replicating from the GTID.slave_pos


current_pos


use this when you do write to the slave and want to increment GTID transaction id
when a master need to become a new slave