The early V6 uBitX was pretty difficult to use on CW and dropped the first part of key elements when starting a transmission. Fortunately, ham programmers jumped in and provided free improved software that corrected the issue. I loaded one referred to as "Reed's sketch" for a friend on his first edition V6, and he went on to use it routinely on CW nets with good success. The problems may have been solved in the latest V6 software, but I still tried the 2 most popular sketches while I had a V6, one by N8ME and the latest version of Reed's sketch. Both have advantages over the OEM sketch and both have nice operating manuals available. I settled on the latest Reed sketch as the one I liked better and enjoyed the rig before gifting it to a friend who lost all his equipment in a fire. I still have both a V4 uBitX and a BitX40 that I enjoy.
Installing new sketches is pretty easy. You need to load a free program called Arduino IDE on your computer0 (I use version 1.8.5) and then download the revised sketches from here or off GitHUB. The Arduino software can compile the programs and upload them to the Raduino through the USB port. It sounds daunting, but it is really pretty easy to do, and you can always go backwards and reinstall the OEM sketch. The new versions read the calibration factors and keep whatever is set, so you don't have to re-calibrate when using them, but if you start from a new Nano you'll have to re-calibrate.
=Vic=
Vic WA4THR