If you have a pvp world with keepinventory true when the player dies he gets a normal shield beacause of the sword-blocking shield!
-Spigot 1.12
-OCM 1.6.1

Wow, I can't believe this bug has gone unpatched for so long! It's now been fixed. Until this latest version gets released, here's a JAR with the patch:

OldCombatMechanics-keepInventory-patch.zip
(Just unzip this, GitHub doesn't support uploading JAR files directly)