iOS Calendar missing items but macOS calendar is fine

Subject says it all, I think. I access my corporate CalDAV calendar system on my desktop and my iPhone, been doing this for the past five or more years. My Mac Mini running macOS Mojave 10.14.4 and my iPhone X is running iOS 12.2. Appointments started to disappear from the iPhone about a few months ago but they still appear on my Mac Mini. I have confirmed that the appointments are indeed there, it's not a case of the appointment being deleted and the Mac Mini not updating correctly, the problem is definitely with the iPhone. I've rebooted the iPhone but the problem still persists. Is anyone else having this issue or knows what the heck is going on? I depend on my calendar for all my appointments so having things not show up is a definite NO NO.