@simpleman
Yeah - I do not mess with that end of things, so I do not know what all of any issues there may be, sorry. I create drum clips in much smaller chunks - mostly no more than 32 measures, and usually more like 8 measures or less.
But I do not believe I have ever tried to go back and edit any converted track, where it seems this truncation can occur. I HAVE gone back in to edit such a converted track, on the occasion where I learned about having to avoid using drum maps when using Step Sequencer. The solution to get me back to where I could edit was to select all of those drum clips on that track and I believe 'bounce' to a midi track, which severed the association with Step Sequencer, creating one giant midi clip with all of the events.
When I went back in to edit that track, I went to Event List and adjusted individual events that way, rather than trying to open it in Step Sequencer.
Good luck with it all - and again please feel free to shoot me a PM with a contact number, in case you want to have me try to help you over the phone to work through any of what I had tried to explain in my earlier posts. I have done this with several other folks over the last few months, including someone from Europe, someone from Hawaii, and one from Japan, so I do not mind communicating in that fashion at all - if that helps you in any way.
Bob Bone