select @@global.gtid_slave_pos, @@global.gtid_binlog_pos,@@global.gtid_current_pos;
https://mariadb.com/kb/en/mysqlgtid_slave_pos-table/
I observe this problem: a Mariadb slave is stopped normally, at a certain GTID, let's call it GTID 'A'. Then it restarts, and for unknown reasons wants to replicate at GTID 'B', where B is previous than A. It is then naturally halted by the gtid strict mode.
The situation will be fixed by a "SET GLOBAL gtid_slave_pos = <GTID A>".