Yes I think that I can probably tell you
Some (only a few in my experience) Amazon browse nodes are more equal than others. Let's call the few less equal ones, "funny" for want of a better word.
I believe that I heard somewhere (but am not certain whether this is true) this is a result of a change at their end.
And I believe that I heard somewhere (but again am not certain that this is true) the funny browse nodes, are ones where the results are generated on the fly based on some kind of internal search at Amazon.
And the upshot is, that as far as I know (again belief not certainty) that the funny browse nodes can't be read in the normal way using the API.
87 - Computer Games - works for me
3448 - Certification - works for me
3508 - Computer Science - works for me
5127 - Applique - works for me
5128 - Basket Crafts - works for me
5129 - Beadwork - works for me
5126 - General craft books - works for me
5130 - Bookmaking + binding - works for me
4198 - Caking baking - works for me
4199 - Chocolate baking - works for me
4200 - Cookie baking - works for me
As do many others (and I've tried at least hundreds and quite possibly thousands)
But there are a handful which don't work
And the upshot is that these funny ones, seem to get no results at all back from Amazon.
I believe that that 1000 is now in the funny category (and has been for a while), whereas I believe it wasn't previously
As far as I know, there is no way to know for sure which nodes are in the funny category except to try them. As I said, the vast majority seem to work just fine.
All the above, is what I currently believe to be the situation, but I haven't investigated this in enough depth to be sure. Except for the part about knowing the vast majority of browse nodes are okay.