Lookup field not working

Lookup field not working

Hi, I've got a couple forms, I work with a work and travel placement company.
One with Candidate info; their name, email, contact info.
The other with their work placement preferences. 

The problem is that when I use the lookup filed to the Candidate Names in the Placement info form, every time I select a few of the names the list sometimes updates with the wring name. Usually the record just before it with the same first name. When I try to edit, I select the right record but when I save it goes back the incorrect record. When I View the form as a Grid it shows up correctly tho.

Any thought?