Steps to reproduce the problem:
log in to PhenoTips and locate a record created in the past
assign a collaborator with edit rights to the record
log out and log in with collaborator credentials
modify the patient record and save --> the last modified date is today (correct)
log out and log in with credential of the record owner
modify patient record and save --> the last modified date is date reported
In the attached screenshots JohnDoe is the owner of the record created on March 6. If JohnDoe modifies the record the last modified date is equal to date created. If Admin or MaryGreen (collaborator) make changes to the record and save the modified date is today.