Blocking is always done "per canvas", that is, a [block~ X] in a subpatch will reblock that subpatch and all its siblings, however it will not reblock the surrounding parent patch. In the patch you've posted, you have two subpatches both with [block~ 1], but the surrounding patch still has the default 64-blocksize. If you try to send something between the two subpaches, they kind of have to pass through the land of [block~ 64] and that's something, Pd seems to dislike.
I still get an output saying "error: throw~ test: vector size mismatch" How bizarre and frustrating!
Is that maybe with a [dac~] or [adc~] in the same patch area? It's not possible to reblock parts of the patch that contain these objects.
I thought of that.. I created a very simple patch with everything block~ 1, nothing connected... As soon as the program opens it gives errors.
It seems to me that throw~/catch~ at blocksizes other than 64 acts weirdly, which is an awful shame because it was almost perfect for my purposes
K