What does "SystemError: <class 'wx._core.CommandEvent'> returned a result" with an error set mean?

When i try to run my experiment, the following error occurred.
wx._core.wxAssertionError: C++ assertion “wxWindow::FindFocus() == GetWindow()” failed at …..\src\msw\caret.cpp(160) in wxCaret::DoMove(): how did we lose focus?

The above exception was the direct cause of the following exception:

SystemError: <class ‘wx._core.CommandEvent’> returned a result with an error set

How could this problem be solved?? Thanks!!!

Have a look at this post for possible solutions.