Records are locked.

I open a Continuous Forms
Pop up = No,
Modal = yes,
Record Locks = No record.
From this form I select a record and open a single form  with 
Pop up = No,
Modal = yes,
Record Locks = No record.
I change a field in single form and now I get a message "Cannot apply the filter because all records are locked". Data is saved so it works but I must get rid of this message. 
I have many other forms where it works but now i have this very strange situation for only this formular. In the Access File Tab I have checked that database is set in shared mode and no locks. 
Best Recards.
omo