Registrations not belonging to event

In my events, registrations from past/deleted events appear again and again. The registrations then have a date which is approximately 10 months in the past. It seems they belong to outdated events.
Even manually deleting old events from the website database does not help. Tried also the maintenance tools of 2.2.0 excerpt the complete deletion of all categories, venues etc.
I am still using JEM 2.2.0 under the current Joomla 3 version. I don't think that the update to version 2.2.2 will bring a change, because I had this bug in the previous version of JEM and therefore I had rebuilt the whole website with new Joomla, database and plugins in the beginning of 2017.

Hi, I am trying to understand:
You had events (now in the past) where there were attending users. There names will be there even when the event is finisthed.
Were / are they recurrent events? If so, perhaps the attending is for the whole serie.
In my case I take an old event, actulize it and save it a new copy (and forget to clean the attending list). Then it's my fault.
(Thanks for giving information about your versions. I am using JEM 2.2.2+ on Joomla! 3.8.3 with ja_purity_iii or ja_simply or protostar.)

Example: There has been an event in March 2017 with several registrations for it. 2 weeks after the end of the event it was deleted.
In January 2018 a new (no copy!) event with a new venue was created. The registration was not activated in this case. Nevertheless, 7 registrations will appear with the registration date of March 2017. Looks like a data base problem?

Hi Dete61,

you're right, it sound like a DB inconsistency.

The registrations will be stored in db table #__jem_register where 'event' is the reference to the event in #__jem_events table. So if you remove (all) events directly on db table you must also remove all corresponding entries on #__jem_register table. Backend's Housekeeping - Delete all JEM data will cleanup all tables.

As far as I can see the daily cleanup - which will delete old events if configured to do so - does unfortunately not cleanup #__jem_register table. This must be fixed, of course. But this should not result in such effects you describe because the event id of deleted events will not be "reused" by database as long as events table is not completely truncated.