iCalendar on iPhone and PC iCloud Calendar regularly unsync, delete events, etc.

I've been using iCalendar to organize my life for almost two years now, and this issue has come up multiple times. At the beginning of each semester of college, I enter my class schedule, regular meetings, work, and other recurring events. As the semester goes on, I add individually occurring events on my laptop and on my iPhone, and the two will sync just fine.

Towards the middle/end of every semester, events will move from 8-9am to 2-3pm for absolutely no reason; I'll check the event details and it still says 8-9am, but it will still show as 2-3pm on the calendar even if I refresh my browser, reload app, etc. Recurring events will also suddenly stop appearing, sometimes they reappear a few days later, or they will only appear two weeks ahead in my schedule still but no longer appear for this week and next week. I'll re-make the event that disappeared and then suddenly both will appear for the correct time, or the original event will suddenly start appearing but at the wrong time on top of the newly-created, correctly-timed event. I may create an event on my iPhone and it never appears on my laptop version.

I have several different-colored tabs and a generally busy schedule, so it is a huge hassle to scrap my calendar and re-fill it out when this happens. I've tried unsyncing and re-syncing my calendar from my phone and it doesn't work. It seems most of the issues are with the desktop version of iCloud, my iPhone iCalendar isn't as affected, but it still has issues. Any insight or suggestions help, thank you!