Cannot delete reminder with date/time alert

Hi,

I use "reminders" quite a bit. I have it synced on my iPhone6 and macbook pro.

The syncing generally works fine although I do get a bit confused between gmail accounts and icloud accounts. But thats an aside...

I have a problem on the mac which is that if I have a reminder on there which is set to alert on a date then repeat (which I sometimes do to make sure I eventually do it), I cannot delete the reminder. So when I have done that task I mark it as complete, it dissappears for a second then the alert is triggered and the reminder is back on my list.

I have tried removing the alert on the reminder, but as soon as I do so the alert is triggered again and it reverts back to the alert with repeat option. I cannot get rid of it!!

I wondered if it was reappearing because it was immediately syncing with my phone again but I have tried deleting the reminder off the mac with both wifi and mobile data turned off and it still happens.

A bug or am I missing a setting?