Access 2010 error when moving focus to subform or acSaveRecord -

so have form in acess 2010 2 subforms manage one-to-many relationship, projects , tasks, bound 2 linked tables on sql server whenever load project, tasks listed on subform.

lately have been encountered error on primary key violation whenever move field on main form area of subforms. tells me primary form trying save whatever loaded, instead of update, it's trying insert.

there no code or event can see (like before or after update) may specific command. there save button on form, button using docmd.domenuitem acformbar, acrecordsmenu, acsaverecord, , acmenuver70 , produces same error.

is there way indicate access use update instead of insert?

i have been looking around don't seem find related fix.

thanks everyone!

edit: have tried removing primary key on linked table , error goes away, suspected, inserting duplicates every time move different record or click on subform. if have clue on record navigation behavior , how configure it, appreciate much!

if there triggers on sql tables, may trigger calling insert statement rather front end.