Short answer first, then the reasoning. 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.

mike_nyc 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.

roxy_nash said:

One order arrived in nine days, one was held at the border for a fortnight, and one came back with a seizure notice.

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.

Adding the clinical framing, because it changes how the question reads.

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

Seized and destroyed — had to get a reshipped package.

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.