Can't really change "cron schedule for retaining snapshots"

Going to Stack Management -> Snapshot and Restore -> Policies you see the "The cron schedule for retaining snapshots is: 0 20,50 * * * ?.
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I can change the cron schedule (via UI or console, doesn't matter) to a different one (say a daily 0 30 1 * * ? for example), but after a few minutes it gets reverted back to the first (default?) one and I have no idea why or how to change it permanently.