Odd "update_virus_scanners" behaviour

[Mike Zanker]

Can anyone think of a reason why the hourly "update_virus_scanners"
cron job should suddenly fire off at 29 minutes past the hour, even
though it has already run on the hour with the other hourly cron jobs?
None of my other hourly cron jobs ran at 9:29, only
update_virus_scanners. It then failed to run at 10:01 with the other
hourly cron jobs.

This is on RH 8.0.

Thanks,

Mike.