Why assembly of each HB Ring takes so long?

After we started completing first production units of HB Rings by late July, we found out that our initially manufactured lighting system did not fit all HB Ring's sapphire housings as intended, due to the tolerances in coating. We looked into possibilities to still fix this and have another set of components manufactured by our supplier throughout August, however we ended up with no other choice than to make custom lighting component for each HB Ring by hand, to make sure it fits all of them. This makes each HB Ring lighting unique, while it enormously slows down the assembly process.