Ok.
Please rename the Synfig configuration folder from your user folder in windows to Synfig2 for example. That would reset all the configuration to the defaults. A new Synfig folder will be created.
Open Synfig Studio and go to Input Devices… in the toolbox.
List here all the devices you can find in the device dialog list. Paste the list here.
Disable all them.
Enable one and test. If it doesn’t work then disable it and repeat with the next one.
You can repeat the same device listing in the same configuration for Gimp. Compare them to see if there are any difference.
Report us here the results.
Good luck
-G