Graph Toolkit variables rarely get instantiated on the canvas on Ubuntu

Steps to reproduce:

1. Create and open a new project
2. Set up the Graph Toolkit example from the documentation
3. Create a graph and open it
4. Create a variable in the blackboard
5. Drag the variable onto the canvas to instantiate it as a node
6. Observe the Graph Toolkit canvas 

Actual results: The variable fails to get instantiated as a node

Expected results: The variable is instantiated successfully every time

Reproducible with versions: 0.4.0-exp.1 (6000.3.0a6), 6000.4.5f1, 6000.5.0b6, 6000.6.0a4

Can’t test with versions: 6000.0.74f1, 6000.3.14f1 (Graph Toolkit unavailable)

Reproduced on (OS): Ubuntu 24.04

Not reproduced on (OS): Windows 11 Pro (25H2)