Go to qb-apartments/server/main.lua, locate the event apartments:server:openStash, and replace it with the following code:
RegisterNetEvent('apartments:server:openStash', function(CurrentApartment)
    local src = source
    local other = { maxweight = 1000000, slots = 50 }
    exports['qb-inventory']:OpenInventory("stash", CurrentApartment, other, src)
end)