On UML Sequence Diagrams floating connectors jump to vertical center

Preflight Checklist

• I agree to follow the Code of Conduct that this project adheres to.
• I have searched the issue tracker for a feature request that matches the one I want to file, without success.

I am opening this bug as a follow-up to #1370 (per request from @davidjgraph.

Describe the bug
The issue is that when I try to snap the second end of a connector to the activation bar, the entire connector gets vertically centered after the snapping completes.

To Reproduce

1. Open Draw.io and create a new diagram with type sequence diagram, delete the initial diagram.
2. Create 2 life lines.
3. Put new activation bars on each of the life lines.
4. Pull a "dispatch" connection onto the diagram.
5. Place the first end of the connection with the blue frame (it correctly snaps)
6. Place the second end of the connection with a blue frame (observe the dashed line, that shows as a preview where the connector will end-up after snapping and note that its vertically centered.

Expected behavior
Expect the connector to "snap" to the target activation bar, according to its current vertical position and NOT to the vertical center of the activation bar.

Screenshots

Test .drawio file

connector-snapping-issue.drawio

Video
https://github.com/user-attachments/assets/aad32f9c-f6b0-4f7f-8ee2-5c786ab11d2a

draw.io version:

• draw.io version v30.3.6

Desktop

• OS: Windows

Start by opening the attached connector-snapping-issue.drawio file in draw.io and reproduce the sequence-diagram steps using activation bars and a dispatch connection. Trace the connector snapping behavior from the reproduction and verify that the second endpoint preserves its current vertical position instead of moving to the activation bar’s vertical center.