Hi,
I just replied to your questions on treddi.com but I will post here again just in case someone find this post.
I tested in Max 2017 and 2018. Both are working fine. I can bake the simulation of more than obe object, one by one and both at the same time. Both hair objects preserve the baked data. Let me know if you need a video showing how I did it.
How you end up doing the simulation? In this case I think the best way is try to reproduce the issue using your scene, if you can share it of course.
I did all my testing using Ornatrix 5.2.9.14704 which is the latest stable build. If there was any problem, it seems to be solved.
Jeordanis Figuereo (Product Designer. EPHERE Inc.)