mech[j] in the flat sorted array hits variant entries (e.g. 'Assassin2 A'
sorts before 'AssassinII' alphabetically, pushing all subsequent chassis
indices off by 1 or more). The script's stock_array[] maps each chassis
index -> its actual position in the flat mech[] array, bypassing variant
entries.
Fix: mech[allowed_mechs[j]] -> mech[stock_array[allowed_mechs[j]]]
Only stock (chassis) names are supported in Mech= field. Operators can
adjust variants manually after Load File is clicked. No rebuild required
(script-only change).