Like apparently many others, I found some quite severe bugs with the rewritten calendar implementation in Moodle 3.3.
In particular, the routines that retrieve events from the DB seem to have hardcoded limits for the maximum number of events to retrieve. This causes all kinds of weird effects (see e.g. MDL-59650, MDL-60131, MDL-60054).
I can fix this temporarily in my local installation by increasing the hardcoded numbers. But that's not a permanent solution, and even a configurable limit for this somewhat arbitrary parameter would seem strange. I am a bit at loss what the intention was here - why are (of the order of) 50 calendar events seen as a good choice for the maximum? Were they supposed to be fetched in chunks?
Can someone from HQ have a look here?