CW is not transmitted when I use my key

[IzzySmith]

I downloaded the cec_0.3QC.packed.bin firmware, and installed it on my UV K5, however when I try to transmit CW with my paddle key, its not always transmitted by the radio, less than 5% of the key presses are recognised. The key works with my Yaesu ft-818nd, so I am pretty sure its either a bug / problem with my settings in the firmware.

I have set:

CW KEY: IA.B
Demodulation: CW

The other CW settings I have left as the default.

Please let me know if you need more information.