The PTTsense mod is required for CW operation. During start up, the firmware tests whether the PTTsense mod is installed.
It was found that the PTTsense mod is not reliably detected on some radios, possibly due to small variations in the hardware environment.
Inserting a small delay in the setup() routine fixes the issue. The extra delay gives the voltages on the Arduino inputs some time to settle at power on.
Improved sketch version v1.28.1 will be released shortly via Github.
73 Allard PE1NWL