Graph Toolkit Port type errors are reported twice (doubled) when the graph overrides OnGraphChanged

Steps to reproduce:

1. Open the attached "GraphToolkit_Repro" project
2. Open the Graph Toolkit Bug Repro window (Window > Graph Toolkit Bug Repro)
3. Under the "BUG 2" section click the "Build A (no override)" button
4. Tick the "Emit as string" checkbox in the "SourceNode" node
5. Observe the Graph
6. Under the "BUG 2" section click the "Build B (empty override)" button
7. Repeat step 4
8. Observe the Graph

Actual results: The "B" Graph doubles the error (shows 2 errors instead of 1)

Expected results: "B" Graph behaves like "A" Graph - one bad wire, one issue, one clear message.

Reproducible with versions: 6000.6.1f1, 6000.7.0a6

Can’t test with versions: 6000.0.0f1, 6000.0.83f1, 6000.3.24f1, 6000.5.11f1 (due to functionality not available)

Tested on (OS): MacOS Silicon Tahoe 26.6.2