^in my opinion the weird substance excrement that can be seen in the wheel pics is the glue that was used to permanently fix the outer wheel to the core. My scenario is that the glue had not properly dried (due to lack of catalyst, presence of moisture, too much glue, bad quality) before the wheels were set up and as the core span inside the wheel, this glue pus got scratched and gathered to wherever it could accumulate and exited the wheel through the first little air bubble (that was created during wheel pouring) that it found. Other scenario could be that the wheel had indeed dried but did not stick very well and because of this the wheel started spinning around the core and the same story follows as above. I do not have a clue what glue is used for this purpose but some glues are mushy even when completely dry so this could be the case with the weird excrement.
edit: The pocket that is visible in the last picture was probably a manufacturing defect and maybe due to excess glue or was even a piece of the outer wheel that actually stuck to the core properly while the rest did not, ripped because it could not hold all the force by itself and the chunk missing got chewed and blended with the glue.
I am curious to find the real cause for this, seems very interesting