In Konsole's src, the action you are doing calls clearHistoryAndReset() (SessionController.cpp) which calls emulation->reset(), session->refresh(), session->setCodec() and clearHistory(). Of all these, the easiest to debug is refresh() which changes the window width by 1 pixel, then waits for some millis and then changes width back to original as a means of a force-refresh hack. So you can see if resizing the window causes you any crash, unlikely though.

The next in line is setCodec(). It may be that it re-sets the encoding and the locale. So you can perhaps try to manually change the encoding and see if crashes?