Calendar won't sync in background on iPhone

I've had this issue for some time and it's incredibly frustrating. My main working calendar is based out of Google. I have it connected to my phone Calendar app fine, however the biggest issue is that it does not Push OR Fetch new invitations or changes to my calendar unless I open up and view the Calendar app manually.

I don't have the option to select Push for this particular account, so I have it set to Fetch, every 15 Minutes, which is the most frequent that I can have it happen. Even with that, I would expect that every 15 mins the calendar would update in the background and I should see new invites appear on my Calendar app, and by extension, update what I see on my Apple Watch.

For instance, I had been showing my first meeting at 12PM today, all morning, despite having several new meetings get added to my calendar for later this AM. If I didn't open up the Calendar app on my phone, I would never see that these 10:00AM or 11:00AM meetings had been added, and reflected on my watch. Really defeats the purpose!

Devices affected by this have been both my previous iPhone 11 Pro, and now my iPhone 12 Pro + Apple Watch series 6. I'd also add that I have attempted to resolve this several times by completely removing and re-adding the account back in on my iPhone.

Has anyone discovered any kind of solve for this?

Many thanks.

Stephen