well , I solved my problem.
after trying to change memory etc etc , I finaly came to see what’s on my oc database. I had 2 records in oc_addressbook for my account (while only one in my nextcloud)
When I created a new one (so 2 in nextcloud) , I had 3 in the table …
I deleted the extra line in the table in oder to remain only the last one
I finaly kept all my addresses in local and remove the sync with nextcloud
then came to nextcloud and delete my contacts
then sync again and import my addresses … and that’s fine !
So that “memory” message what just a bad way to search
Don’t know how and why I had the extra oc_addressbook line … 
only my account on my nextcloud …
I of course deleted all the oc_addressbookchanges related to the oc_addressbook I deleted
If that can help someone …
and to say the truth, I didn’t apply this post solution as suggested …
I didn’t find this kind of solution usefull … … 
