Nylas keeps transactions for objects for two weeks, however we are not privy to each change a transaction made to an object.
To explain why an object might change, client or provider side tools are the typical causes:
- Applications such as time management tools such as (i.e. clockwise) can change the times of events.
- Provider side settings may not allow the creation of events and delete them after successful creation.
For the above scenarios the user or the Mail administrator would be able to provide more details.