Trying to assemble a moonsilver pendant, have added so far 1 moonsilver chain, 1 platinum chain, 1 unembellished ring, 2 sapphire chunks, 2 ruby chunks, 2 onyx chunks. Study and it says that it needs 2 additional unembellished rings:

You study the incomplete collection and determine the following pieces will be required to complete it:

2 Unembellished Rings

However when I try to add the rings it says:

assemble unembellished ring with unfinished collection
The an unfinished collection does not require any more pieces of that type.

Was told to submit a bug report here.