done some moire testing with the following hope this helps
Created simple Table
ID – auto increment primary key
T1 – text 80 long
T2 – text 30 long
Used option to create database pages, did this , changing ID to hidden and including all fields on all reports (ex search)
Results opened up, no records as expected,
insert entered text in T1, pressed insert,
record added as record #1
update filled in details T2, pressed update
got blank details page saying
This record been removed,
ID now changed to #0
results showed details of #0
update more changes made all worked
insert added new record ID #2
update #2 Duplicate entry 0 for PRIMARY
added further records , tried to change, with same results
next test
truncated table
added 3 records
the first record to be updated its ID id changes to 0 , and its only this record that will accept changed yet more records can be added.
Hope this helps
nb verified ID's with Navicat