Hello! I just wanted to let you know that our team is experiencing a similar issue right now with a large number of events on the calendar.
We are seeing typing issues when trying to enter the name (it will lose data as we type) and save.
We are also seeing data being lost such as selecting a host for an event, it will save, but then the host will be removed from the event.
Hi there, @user9181 and welcome to the Community 
Could you please share your widget ID? I’ll be happy to check it for you 
The widget ID is 5cd9b582-3f6e-498a-84c2-c6f17e9a1da1
We believe the main issue is that multiple people were trying to edit the widget at the same time (different events or general calendar formatting), and their changes were overwriting each other.
We also noticed that the network request triggered to save the widget sends the FULL widget configuration (including every event in the calendar) every time, rather than allowing granular updates to individual parts of the widget. This prevents multiple users from working on the widget simultaneously.
One option we hoped for was to disable the auto-save feature entirely. When creating a new event, we would prefer to edit it locally and trigger a save when it’s finished, rather than dealing with the auto-save feature causing issues while editing.
Ah, I see! Yep, this issue might occur because of the simultaneous editing by multiple users. Unfortunately, there is no way to change this behavior now, but I’ve added this idea to the Wishlist on your behalf - Let multiple users edit the same widget simultaneously
As for the auto-save feature, it’s impossible to disable it now, but a request for this is already on the Wishlist. You can upvote it here - Stop auto saving in widgets