This is a difficult question to answer to without seeing configuration, implementation and which reports you are running but anyway here are some of the things that I would check:
Check that both report suites have the same configuration for event1. Check that both are same type (counter or currency or numeric) and that both have the same serialization settings (record all the time or once per visit ...) (under admin>> report suite >> select report suite >> Edit settings >> Conversion >> Success Events)
Check that there is no VISTA rules (Contact ClientCare) or Processing rules (under admin>> report suite >> select report suite >> Edit settings >> General >> Processing rules) that affect event1.
In terms of implementation are you using multi-suite tagging ? If yes check that both report suite Ids are present in the same server call as event1. You might want to drill into your data to figure out where the discrepancy happens, like on which page, on which custom, download or exit link.
Ultimately if you think the configuration and implementation is correct, then extract data feed for both for a day and mine the data to see if you can figure out why the events are missing in one report suite but not the other one