Cron jobs - only 3 actually working, rest are playing up

[iTypeR]

Hi,

As with many of you I have many cron jobs in the scheduled task list.. 21 to be exact.

Problem is that only 3 of them are running as per the options selected. Others don't run at all, and some (like twice-hourly infractions cleanup) run once a week or just randomly.

I've spent a week trying to isolate the problem but have really come to a dead end. Any suggestions how to troubleshoot this?

thank you in advance!