Right off the bat it looks like you have sinned by having only one disk, adobe requires a minimum of two and anyone here will tell you that that is not optimum.
The next problem is you even mentioned Matrox in a Premiere forum, they historically just do not mix.
WHY doe Adobe STILL refuse to put back in stop motion capture ?
Purely a guess but probably because not enough people use/ask for it.
Why has Adobe screwed up the whole export thing and made it not only 100 times more complicated, but, also able to do 100 times LESS than it always used to in previous versions ?
I find I can get a LOT more work done in the same amount of time with the new AME.
why are my...exports...repeatedly failing - unknown error?
That's a tough one. This error has been around for years, and to my knowledge, there just is no predictable cause for why it happens. (Hence the 'unknown' part.) Which unfortunately means there's no predictable fix for it either.
I didn't sin, but you did by assuming things that are not true.
1/ The project file is on the same drive as the export, BUT, the source files are on a different capture drive than the export to C.
2/ I've been using the Matrox RTX100 with previous versions of Premiere for 7 years, and the two have worked very well together all that time, and still are working very well, and, will continue to I've no doubt. - Just because you couldn't get it to work, does not mean they don't.
3/ The export I refer to did not have any connection to the Matrox box. All Premiere and Encore.
4/ I didn't mention that I had done a lot of successful export tests of various definition formats, to other formats, and including a 1 hour Full HD export, no problems.
So, - there - nyah !
thanks for trying to assist Jim.