Thanks for the detailed writeup @mgtmn! I’ve seen a similar report about zero-length billing cycles when using multiple anchors - this unanswered thread describes the same symptom with Cycle #2 having an end date before the start 
To dig into this properly, could you share the GraphQL mutation you used to create the selling plan (with the billing/delivery policy config), plus an x-request-id from the response headers? That’ll let me check our logs and try figure out what exactly is happening here