It has been rumored that this is caused by a failed IC. My guess would be U25, a 74LCX541 buffer. This is located on Page 1 of the
Angelia Schematic, reference block B3.
However, it is odd that there are all of a sudden a lot of people reporting this issue. One wonders if people have been just sitting on this issue, not complaining about it, and, now that someone has mentioned it, more people are piping up.
Obviously the only way to determine if IC is failed is to put an oscilloscope probe on the outputs and see if any are stuck.
The only other reason I can think of is that there is something funky about the timing closure of the firmware where the keyer function is concerned, and therefore the issue only shows up on certain serial number radios where the FPGA is an edge case. Or, perhaps something has gone a little wrong with the voltage regulation into the FPGA and that has changed its timing closure.
But those latter issues are all "zebras": rare, unusual and unlikely. Check the "horses" first: software, firmware (which you undoubtedly have), then the connector and U25.
73,
Scott