CheckMate makes a lot of OEM mags for a variety of 1911 makers, and there are a lot of 1911 makers. The supply line seems to have had a lot of kinks in it over the past year or two.
Note all the "out of stock" CheckMate varieties at a top CheckMate retailers such as Top Gun Supply
https://www.topgunsupply.com/magazines/1911/check-mate.html
There is something to be said for the easy availability of mags from places like Wilson, McCormick, and Tripp. However, I don't even know if any of those companies actually make the mags with their own stamp on them. Of course, CheckMate has such a wide variety of mag styles it's probably hard to keep all of them in inventory.
The owner of Thunder Mountain Custom (
http://shop.1911parts.com ), another big retailer of CheckMate mags, has commented CheckMate is concentrating on one particular mag (I can't remember which, but suspect it was their hybrid lipped 7 rounders), and every direct order they get from an individual for something else jams up their supply line and makes if difficult for the retailers to get the mags they want.
I encourage folks, if you like CheckMate mags, order them from a retailer like Top Gun Supply, Thunder Mountain Custom, Joe's MagMania, or even those from CMP (if that is the mag you want), and not from CheckMate direct. CheckMate is a fine manufacturer, but retail isn't their strong suit.