Hello, I would like to report that I have encountered this issue and found a resolution which did not require wiping my settings/preferences.
I was able, through some head-scratching moments, to find the offending setting causing the drum map notes to disappear. I will attach a screenshot. Essentially, the “Instrument Viewer Width” field I have highlighted was set to a negative value. I entered a positive value for that as well as the below H and V values (also highlighted) and my drum map notes came back!!
I hope this helps anyone else who comes across this post trying to solve their issue.
