How to force sync between iPad and iPhone for tasks?

Hello

I am having a weird issue that I can't solve. I created a bunch of repeating tasks which show correctly on my ipad and iPhone. However when I mark these complete on one device the update is no reflected on my other device. If I mark the one complete on the second device then the first device where it was marked complete ends up with two completed tasks. Only one new one is generated.

How can I fix this? It is super annoying

Thanks