I dont know what causes it. I have the latest versions of SuperBLT and BeardLib and i got Optimized Marshall Shields to see if that was the issue but no.

Here's my Crash Log: (Note: I was doing this on Proving Grounds since Enemy Spawner doesn't have the Marshalls)

Application has crashed: C++ exception
[string "lib/units/equipment/shield/shieldbase.lua"]:138: attempt to index field 'flash_shields' (a nil value)

SCRIPT STACK

spawn_unit() =[C]
_chk_spawn_shield() lib/units/enemies/cop/copinventory.lua:70
add_unit_by_name() lib/units/enemies/cop/copinventory.lua:28
add_weapons() lib/units/enemies/cop/copmovement.lua:598
post_init() lib/units/enemies/cop/copmovement.lua:529
post_init() lib/units/enemies/cop/copbase.lua:64
lib/units/enemies/cop/copsound.lua:17
safe_spawn_unit() =[C]
produce() lib/managers/mission/elementspawnenemydummy.lua:77
on_executed() lib/managers/mission/elementspawnenemydummy.lua:149
execute_on_executed() core/lib/managers/mission/coremissionscriptelement.lua:210
_trigger_execute_on_executed() core/lib/managers/mission/coremissionscriptelement.lua:147
on_executed() core/lib/managers/mission/coremissionscriptelement.lua:131
on_executed() lib/managers/mission/missionscriptelement.lua:24
call() core/lib/managers/mission/coreelementunitsequencetrigger.lua:57
runned_unit_sequence() core/lib/managers/mission/coremissionmanager.lua:212
activate_callback() core/lib/managers/coresequencemanager.lua:2817
activate() core/lib/managers/coresequencemanager.lua:2023
run_sequence() core/lib/managers/coresequencemanager.lua:2484
run_sequence() core/lib/units/coreunitdamage.lua:1224
run_sequence_simple3() core/lib/units/coreunitdamage.lua:1220
run_sequence_simple2() core/lib/units/coreunitdamage.lua:1216
run_sequence_simple() core/lib/units/coreunitdamage.lua:1212
interact() lib/units/interactions/interactionext.lua:722
interact_start() @mods/The Fixes/useinteractionext.lua:8
interact() lib/managers/objectinteractionmanager.lua:87
_check_action_interact() lib/units/beings/player/states/playerstandard.lua:2480
original() lib/units/beings/player/states/playerstandard.lua:1046
_update_check_actions() @mods/base/req/core/Hooks.lua:264
update() lib/units/beings/player/states/playerstandard.lua:446
original() lib/units/beings/player/playermovement.lua:279
@mods/base/req/core/Hooks.lua:264