Taking the question as asked, rather than the general version of it. The pattern that distinguishes a bad batch from an exit is behaviour rather than product. A bad batch comes with communication, a reshipment offer and a batch number. An exit comes with slower replies, pressure toward less reversible payment methods, sudden discounting, and the same reassurance repeated without any new information. The product tells you less than the correspondence does.

LabKate said:

The pattern that distinguishes a bad batch from an exit is behaviour rather than product.

Right, and one flattering data point from a group buy is not consistency. Consistency means separate batches, separately commissioned, over months.

DadBodDave said:

Living somewhere the domestic route does not exist, which makes most of the advice on this board inapplicable to me.

Agreed, with a caveat about community reputation: it is a lagging indicator. Reports arrive weeks after orders, so a supplier can look excellent for a month after quality has already changed.

From the other side of the consultation, briefly.

International shipping tracking for cross-border ordering orders: my experience with customs in the US when ordering from overseas:

Package cleared customs in 2 days, no issues.

Tips: always include a copy of your prescription, declare medication properly on customs forms, keep quantities reasonable (personal use = 3 month supply max), and use a vendor who has experience shipping to your country.