18 was my LOI for a funny reason. I saw the solution, and despite the unfamiliar usage figured it had to be correct. But I had mistyped 20a, which implied that the 2nd and 3d letters would be "OO"...which was remotely possible but I couldn't believe. Finally saw the typo and finished.
The long anagrams in particular cost me a lot of solving time and made this a slightly harder than usual Everyman.