As a data point, please try adding --offline to your image building command lines (e.g. put it in ...COMMON_ELEMENTS...). This affects cache invalidation / liveness checks (specifically turns off checking for up to date images, and turns off having pyp.python.org as a fallback index).
As a data point, please try adding --offline to your image building command lines (e.g. put it in ...COMMON_ ELEMENTS. ..). This affects cache invalidation / liveness checks (specifically turns off checking for up to date images, and turns off having pyp.python.org as a fallback index).