Slok operated 737-200s in Nigeria recently (this year), until one of their pilots busted the ILS minimum and their AOC was revoked. They were also operating 4 732s instead of 2 as per AOC. these are the reasons the Nigerian CAA gave.
But most people believe it was a political move since the owner (Anambra State Govenor) is involved with a feud with the chairman of the leading political party.