NINJAM uses a really cool collection of time-coded .ogg files to record jams in an extremely compact format. It's not a very usable format in its original form (lots of tiny OGG files named with unintelligible UUIDs in many separate folders, all summarized in a clipsort.log file that contains timecoding and other metadata), but it's quick work to take a folder of NINJAM files and open the clipsort.log file in Reaper. Reaper reassembles the whole thing into a multitrack Reaper project, with consolidated WAV files for each performer. The resulting WAV files can be many GBs, vs the 100MB or so that the OGG files might represent. Very cool stuff.
The gotcha is that you have to set some time period in the NINJAM server configuration for when it should stop writing to one folder and start writing to a new one. I chose a 2 hour period. What I didn't know is that each performer's track may stop in one folder and start in another one at slightly different times. So, this means if you try to heal up two sessions by just bumping the end of one up against the beginning of another, you're leaving a gap. They're more like jigsaw puzzle pieces, need to get the ends of each individual track lined up with the beginning of another. A bit more fiddly than rendering each folder to a stereo track and butting those two rendered files against each other.
Live and learn. Mostly learning that it's best to let @ikjoyce do this task.