For some odd reason my htaccess was banning some Bingbot and Yandexbot crawls, but there were others, such as University of Toronto, and I could not figure out why. I blamed my host provider, and I was incorrect. There was no other cache of IP blocks. It turned out to be, as usual, a user error. My user error.
Through the course of repeatedly bisecting my htaccess, I went through with my patient Big Weed, 12 times, until I isolated the errant code. It turned out to be syntactically correct but logically incorrect. As the syntax was fine, it passed my two htaccess syntax checkers. The error was, in CIDR format: