AWX advanced schedule

If possible,
I’d want to have a schedule like: Run every Saturday, from 2am (12 occurrences) like from 2am til 2pm, with a 30 minutes interval: 2am, 2:30am, 3am, 3:30 am… and so on…

This seems to run OK for 1st Saturday, for the next occurrence, it runs ONLY once , 17.01 and again ONLY once on 24.01…
Am I missing something … or some other approach to to achieve this ?