Impressions are flat, average position went 2.4 to 9.1. So it is a genuine slip.
We do have March and May crawls. Just checked and internal links to that URL went from 31 to 9 when we retired an old category hub in May. Well then.
Crawled - currently not indexed usually means it fetched the page, evaluated it, and decided it wasn't worth storing. Duplicate manufacturer copy across 300 URLs is the textbook cause. You don't need 300 essays. Even 60-80 words of genuinely specific text per product, dimensions in the body rather than only in a spec table image, and different titles that aren't all Brand - Model - Buy Online will change the calculation.
Then the location variants are a separate decision from the rest. If you have real local presence, keep them and make them genuinely local. If not, one page.
Weigh whether the 40 map to genuinely different searches or to 8 searches expressed 40 ways. Export every query each page ranks for, dedupe, and see how many distinct intents you actually have. In every version of this I've done, the answer came out around 10-12 real intents and the rest were the same thing with a city name or a synonym swapped. Consolidate to match the intents, not to match your calendar.
When I merge I keep the older URL as the surviving one, because it usually has the links and the history, and 301 the newer one into it. People instinctively keep the newer, better-written page and then wonder why the merged article underperforms both.
Check what queries you're getting impressions for. If they're wildly off topic, the pages aren't clear about what they answer. If they're on topic but you're at position 40, that's normal early-site behaviour and it will creep up. Very different problems that look the same on a graph.