Replication using GTID and MASTER_USE_GTID=current_pos easily breaks when a transaction is generated on the Slave and Replication is restarted.
It happens if the transaction generated on the Slave is the last before issuing START SLAVE,
so even after the replication was already stopped.
To recover you need to switch to slave_pos gtid mode.
I also noticed a non consistent numbering of GTID, but it's not related, the trx_num part of GTID for transactions generated on the Slave is increased by one in respect to trx_num of the latest GTID received from the Master.
So you can have:
I don't know if it's on purpose, but it does not seem consistent to me, at first impression I'd make each server having its own trx numbering with no holes.