Posted 22 October 2014 - 07:48 AM
Welcome to the hazzards of owning lots of mechs.
It's a known issue. Each of your mechs has a designated config number for storing weapon groups locally. Occasionally, one of your mechs will be assigned a number that matches one you already have, and they'll share weapons groups, which means when you set one, you reset the other.
For example, my Kit Fox-S (my most played Kit Fox) and my Raven 3L share a config. This is rather annoying. I have 2-3 other mechs that share a config number.
Honestly, the best fix would be for PGI to reset all the desgniations (which would delete all your weapon configs unfortuantely), renumber all your mechs, and then increment the mech designation based on total mechs purchased, so they never will have the same number ever again, (IE, if you own mechs 1-9, sell #8, the next one you buy is still mech 10).