Hello,

If I press the key "Alt-Shift-F" with script it crash all times. I reproduces the same crash with Python 2.7. 
To reproduce it, on terminal osx 10.13.6 (17G3025) : 
- run "python3 ScrollFrame.py" 
- Click one time on tk window (it show on foreground)
- Press "Ctrl-Alt-F" (all other alt produce the same crash)
- And you obtain the crash next :

The crash on python 3.7 :

2018-11-10 11:50:30.702 Python[3095:292595] *** Terminating app due to uncaught exception 'NSRangeException', reason: '-[__NSCFConstantString characterAtIndex:]: Range or index out of bounds'
*** First throw call stack:
(
	0   CoreFoundation                      0x00007fff2b04123b __exceptionPreprocess + 171
	1   libobjc.A.dylib                     0x00007fff522d2c76 objc_exception_throw + 48
	2   CoreFoundation                      0x00007fff2b0d2d5d +[NSException raise:format:] + 205
	3   CoreFoundation                      0x00007fff2afbd236 -[__NSCFString characterAtIndex:] + 102
	4   Tk                                  0x00007fff37721343 TkpInitKeymapInfo + 731
	5   Tk                                  0x00007fff377271a1 Tk_MacOSXSetupTkNotifier + 798
	6   Tcl                                 0x00007fff37621a50 Tcl_DoOneEvent + 300
	7   _tkinter.cpython-37m-darwin.so      0x000000010dd957ac _tkinter_tkapp_mainloop + 256
	8   Python                              0x000000010d3d4f42 _PyMethodDef_RawFastCallKeywords + 525
	9   Python                              0x000000010d3d981e _PyMethodDescr_FastCallKeywords + 82
	10  Python                              0x000000010d46b1a2 call_function + 615
	11  Python                              0x000000010d4622ec _PyEval_EvalFrameDefault + 2579
	12  Python                              0x000000010d46bad1 _PyEval_EvalCodeWithName + 1837
	13  Python                              0x000000010d3d4474 _PyFunction_FastCallKeywords + 225
	14  Python                              0x000000010d46b17a call_function + 575
	15  Python                              0x000000010d462305 _PyEval_EvalFrameDefault + 2604
	16  Python                              0x000000010d46bad1 _PyEval_EvalCodeWithName + 1837
	17  Python                              0x000000010d461851 PyEval_EvalCode + 42
	18  Python                              0x000000010d490a5f run_mod + 54
	19  Python                              0x000000010d48fa7a PyRun_FileExFlags + 164
	20  Python                              0x000000010d48f159 PyRun_SimpleFileExFlags + 283
	21  Python                              0x000000010d4a6842 pymain_main + 5114
	22  Python                              0x000000010d4a6fd4 _Py_UnixMain + 104
	23  libdyld.dylib                       0x00007fff52eec015 start + 1
)
libc++abi.dylib: terminating with uncaught exception of type NSException
Abort trap: 6

The crash on python 2.7 :

2018-11-10 11:51:34.728 Python[3104:294757] *** Terminating app due to uncaught exception 'NSRangeException', reason: '-[__NSCFConstantString characterAtIndex:]: Range or index out of bounds'
*** First throw call stack:
(
	0   CoreFoundation                      0x00007fff2b04123b __exceptionPreprocess + 171
	1   libobjc.A.dylib                     0x00007fff522d2c76 objc_exception_throw + 48
	2   CoreFoundation                      0x00007fff2b0d2d5d +[NSException raise:format:] + 205
	3   CoreFoundation                      0x00007fff2afbd236 -[__NSCFString characterAtIndex:] + 102
	4   Tk                                  0x00007fff37721343 TkpInitKeymapInfo + 731
	5   Tk                                  0x00007fff377271a1 Tk_MacOSXSetupTkNotifier + 798
	6   Tcl                                 0x00007fff37621a50 Tcl_DoOneEvent + 300
	7   _tkinter.so                         0x00000001026cca77 Tkapp_MainLoop + 354
	8   Python                              0x000000010236a357 PyEval_EvalFrameEx + 19822
	9   Python                              0x00000001023653d2 PyEval_EvalCodeEx + 1562
	10  Python                              0x000000010236e4d7 fast_function + 290
	11  Python                              0x000000010236a25a PyEval_EvalFrameEx + 19569
	12  Python                              0x00000001023653d2 PyEval_EvalCodeEx + 1562
	13  Python                              0x0000000102364db2 PyEval_EvalCode + 32
	14  Python                              0x000000010238679b run_mod + 49
	15  Python                              0x0000000102386842 PyRun_FileExFlags + 130
	16  Python                              0x00000001023863c4 PyRun_SimpleFileExFlags + 706
	17  Python                              0x0000000102397f44 Py_Main + 3136
	18  libdyld.dylib                       0x00007fff52eec015 start + 1
	19  ???                                 0x0000000000000002 0x0 + 2
)
libc++abi.dylib: terminating with uncaught exception of type NSException
Abort trap: 6