"FxFactory is a store that controls the sale, installation, and organization of plugins. They are not FxFactory's plugins. They don't write any code for the plugins."
This is your statement. And it's just not true, Tom. THE FX FACTORY PRO Plugin package which I specifically gave you a link to is code written by FXFACTORY, hence the name. Noise Industries did indeed "write the code" for those plugins. And if you take any of those transitions, specifically ALL of them, they don't work anywhere except on the primary magnetic timeline. But since you're having such a tough time understanding and are a stickler for specifics, here's a video demonstration:
https://www.youtube.com/watch?v=W_tikm9mx8E
On primary timeline,The FXfactory Pro transition works. On secondary timeline, same clips, same transition, they do not. It's like it's not even there.
The same problem is happening with ALL, specifically ALL, of the transitions offered by Industrial Revolution. It is also happening for all, specifically ALL, of the Nattress transitions and all, specifically ALL of the Luca Light transitions. Not effects, just transitions. I will not speak for any of the other ones on the FXfactory portal, but I can say with confidence that currently the above listed do not work on a secondary timeline.
When a problem is this consistent and this widespread, rather than make every third party developer figure out the same issue, maybe Apple should look at it and say, hmm, maybe our new code is not playing nice with many of the contributors who add value to our program.
If you have a real answer, other than basic stuff like, "I hoped you backed up the old version", or "you should contact the third party", or more half wrong misinformation, I'd love to hear it. Or maybe you can find somebody who actually knows what they're talking about, that's cool too.