Problem with keyboard inputs using CTRL + key

[AndyRR]

I would like to smoothly pan a graph by pressing Ctrl + arrow key (this is used e.g. in Inkscape to pan the view). My program is monitoring which keys are pressed. If the Ctrl key and an arrow key are pressed then the panning starts and should continue until keys are released.

The problem is that if I use a Ctrl + key combination the action stops after a fraction of a second. However if I replace Ctrl with e.g. the key “A” , there are no problems with the action stopping before keys are released. Is Windows preventing Ctrl to be pressed for too long? Shift key is behaving similarly as Ctrl. Thanks in advance for any help.

Sample code that demonstrates the problem as attachment and as a screenshot below: