Thanks very much for sharing this!
I didn't see the missing track or crash issues that you described, but since my system is similarly afffected by gawdawful lags when working with lots of titles, it is
very slow to respond. I have some screen recordings showing just how slow my 8-core/16-thread CPU is with this project, but I'd like to focus more on workarounds to help you get back to editing.
In this OneDrive
folder, there are 3 new projects and a produced version of your track 1 and 2 clips
without any titles. When you open the projects, you may need to point PD to where your original clips are located since I didn't want to pack them again on my side.
Rev1 has the first 2 sets of titles combined into just 2 title tracks. On my system, previewing them is somewhat quicker than in the original project where the contents were in 5 or 6 separate tracks.
Rev2 gets rid of the edited content on tracks 1 and 2 and replaces it with a produced version of the same content. On my machine, this eliminates almost all of the terrible performance, even though the titles are in the original configuration.
Rev3 combines the above projects, so it's a produced clip along with condensed titles, and this gives me the best performance.
One other thing I found was that if I changed the preview mode from Real-time to non Real-time, playback was much quicker (although still a little slower than actual speed), even in your original project. You can't hear audio in non Real-time mode, but it may be a good choice for editing when you don't need to have sound.
Please give these revised projects a test drive and let us know which ones (if any) improve your system's performance.