Unreliable and unpredictable calDAV syncing with Mavericks Server

I have a Calendar server set up using Mavericks Server 3.2.2 with a single user account. It syncs purely between Week Cal on my iPhone running iOS 8.4.1 via a computer-to-computer wireless network, and BusyCal on the host MacBook Pro.

Lately it's become very unreliable. A good example just occurred, where two events that I had created on my iPhone were synced to the server, but two things went wrong:

1) Whilst both of the events were in the same calendar on the phone, they turned up on the Mac as two different calendars - one was the same, one had changed.

2) One of the events was deleted from the phone during the same sync procedure. It has not reappeared during subsequent syncs.

Another example is a recurring event set to start on a given date, and "end after 4 times" (BusyCal)/"After 4 occurrences"(iPhone). This event has four occurrences on BusyCal on the Mac, as it should, but only 3 on the iPhone - the last occurrence is missing.

Where do I start with troubleshooting this issue?