I've come across an issue where The Summoner on Nightmare doesn't drop a Catalyst of Learning for a character crated on Sigma 1.0 while not having any item filtering tools installed. Things I have tried so far:
1. Deleting the D2Sigma.dll and MXL.mpq, then re-patching from the launcher.
2. Removing Median XL entirely and Diablo then reinstalling both while leaving only the data folder to preserve the character.
I could be missing something obvious so any suggestion would be appreciated so I know whether or not I should report this as a bug.