Adeel, thanks for looking into this.
Here is some more info for you:
I deactivated Breeze and installed W3 Total Cache and the event entry form worked fine with that. Figured I keep it that way until I heard back from you. But I saw another user on the Cloudways forum said they have no problems with Breeze and All In One Calendar, so I decided to deactivate W3TC and activate Breeze again, and it worked, no problems on the form.
So I did the same thing on the second website that was having the same issue, and it is working now there too. So I have NO idea why that would be, since nothing else changed.
For the record, I was having this problem on two different sites, one of them I deactivated all plugins except Breeze and AI1Calendar, and was having the same problem. But now it seems to be working fine on both sites.
I’ll keep an eye on it and report back if there are any more problems with it.