ErrorOccurrenceTimeSPanTooBig: A recurring appointment could not be migrated because its time span is too large. For example, a recurring appointment scheduled to occur every day but with a duration of two days may trigger this error. Recurring appointments with a reminder or due date outside any possible occurrence may also trigger this error.
The appointment will not be migrated because it is invalid. Changing the appointment's properties to be valid may allow it to migrate successfully. Resubmit the migration if it failed, or submit your mailbox in Retry Mailbox Migration Errors mode after the mailbox has successfully migrated.