Startup error for all cron based rules

The startup error has been removed, but for some reason the rules appear to run multiple times e.g. rule

   Time cron "0 * * * * ?"

runs once a minute but each minute runs the code more than once (often 3 times) very quickly. I have a tag inside the code which is increment each time run and this increments by up to 3 each minute.

If you edit the rule, then it resets it and runs correctly. If I restart openhab or reboot raspberry pi, then it runs multiple times each minute.