Thank you for the post.
I am not able to replicate. To attempt to replicate, I performed the following steps:
1. New Database
DATA (PK) -------< UI (fk)
2. Added four records to Name Field: One, Two, Three, Four
3. On the UI layout, created a portal with all 4 records
4. Placed a Pop-over button in the portal
5. Placed the Name Field in the Pop-over
6. Hosted the file with FileMaker Server 13.0v3, enabled for WebDirect
7. Accessed via WebDirect > Clicked the Pop-over button on row one, Name Field reads "One"
8. Changed "One" to "Edited"
9. Closed the Pop-over
Result: "One" now reads "Edited"
Please let me know if I am missing a step to replicate.