We fixed a few parts related to static call and also external call, on my development version it seems to work fine.
Is it still occuring with latest release 6.0.6.8510 (patched regarding the FUNCTION class file, and ecdbgd executable)  ?

Can you try to step into, and evaluate expression the "{EV_GTK_EXTERNALS}.gtk_set_locale"
Is it also crashing the debugger ?