Is any one know how to fix it?

It happen only when 3 or more user working on the same form and one user updating a table. Very often the other users' screens automatically update after the first user saves data. I make sure the key field use unique value with sys(2015) function on master table and copy the unique value to child table. But it didn't work.

It not just happen on one form but many form using the same type of buffering as following.

Master table Optimistic row buffering
Child table use Optimistic table buffering