Item link tooltip requires double-click on first use

[refaim]

Description

Clicking an item link in a WIM message window requires two clicks to show the tooltip the first time. After the tooltip has been shown once for a specific item, subsequent clicks on that link work with a single click. New (not yet clicked) item links still require a double-click.

Steps to reproduce

1. Receive a whisper containing an item link
2. Click the item link in the WIM window
3. No tooltip appears
4. Click the same link again — tooltip appears
5. Click the same link again — tooltip appears (single click works now)
6. Click a different item link — no tooltip (requires double-click again)

Notes

• This does not happen in the default chat frame
• The issue is likely related to OnMouseDown calling StartMoving() on every click in the ScrollingMessageFrame (WIM.xml:327), which may interfere with ShowUIPanel(ItemRefTooltip) in the SetItemRef call chain
• Attempted fixes (skipping OnMouseUp focus logic via flag, replacing StartMoving with RegisterForDrag) did not resolve the issue