IF you were last working on the module tab (used for frequently swapping in and out modules) when last working in the mechlab (or playing the game)... the next time MWO is launched AND you go back to the modules tab... it appears all the weapon modules are not prefiltered.
What I mean by prefiltered, I mean the "mounted weapons" option is checked. It doesn't behave that it was checked until you look @ the mech again.
Edited by Deathlike, 18 August 2015 - 02:25 PM.