Recent one for me:
My original city plan for Ch. 11 included building a few new Festival Merchants to supply me with additional seeds. I started Ch. 11 at the beginning of December, and over ~2+ weeks I didn't see a single Festival Merchant in the MA. I made sure to check every natural refresh (but did not spend any diamonds to refresh, because that seems wasteful). I even went a while not crafting anything in MA, so that I wasn't "occupying" a slot during refresh and nerfing my chances at a Festival Merchant popping up.
So, the Elvenade Logistics Center was available in this event, and while it's inferior to the Festival Merchant from a seeds/sq perspective, it seemed like the solution to my problem. When it came up as the daily prize, I decided to dump my keys into it -- I needed seeds! -- and ended up with 8 of them.
Immediately after I dumped my keys into Elvenade Logistics Centers, the next refresh of MA had a Festival Merchant. As did the next one. And the one after that. All told, in the 6 days since I got all those ELC's, I've seen 9 Festival Merchants in my MA.
So, now I have 8 Elvenade Logistics Centers and 5 Festival Merchants, not all placed yet, but once I reorganize some stuff and get them down, I guess I'll be good on seeds