Ok, but for CB-Emu I've already found a simple fix:
With the debugger I saw that m_inp_mux is 0x70 while the program is thinking, and in this state all (white) keys in the left column have no effect (except this buggy CE which causes a crash).
So I just ignore ALL these keys (incl. CE) by adding the following line in read_inputs() before the 'return data;':
if (m_inp_mux == 0x70) data &= 0xfe;