Performance issues with calendar from Office365

I use khal for multiple vdir calendars: work, private, academic, etc. I experience serious performance issues with khal interactive, where jumping to the next week usually takes up to 2 seconds.

I pinpointed the issue (as already expected) to the work Office365 calendar I sync via vdirsyncer and davmail. I don't know if it is the sheer size of some events or the format of the .ics files that produces this issue. If I disable this calendar, my other calendars work just fine.

I used the discover type for many folders, but even when I disable all other calendars and explicitly define my work calendar with the respective vdir, nothing changes. So this is not the cause.

Now this issue alone would be bearable if khal cached the interactive view. What makes it so painful is that this happens on every restart of khal interactive. Is caching just broken for me or is this default behaviour?

Anyway, I don't know how to get to the root cause of the performance issue. Any help on how to further debug would be appreciated.

Start by reproducing the delay in khal interactive with the Office365 work calendar enabled and disabled, then investigate whether the interactive view is cached across restarts. The issue provides no file or test entry point; done would require identifying the performance cause or confirming and fixing the caching behavior.