In the attached song, I am getting clicks when the same instrument is used on different tracks. If I duplicate the instrument and use the new instrument on the second track I don’t get clicks. Is this normal?
Your instrument contains a DSP effect chain. By default, all of the samples are being processed through this single DSP chain, effectively condensing everything down into a single audio stream. This single audio stream may only be played on a single track at any given moment, which is similar to how we treat VST plugins which only have a single output.
Since you are playing your instrument on multiple tracks simultaneously, the click comes from Renoise attempting to prioritise the notes and switching the audio output from track to track on the fly.
You can prevent this by putting all of your notes into a single track instead.
Alternatively, you can modify your instrument to give it multiple DSP chains, then map the different samples to different chains, and then route those chains to different tracks as needed. (Routing is only possible in 3.1 at the moment.)