Sound lag in big battles

[yuser]

I have a quite strange problem. In big battles sometimes sound starts to lag. In the worst cases I can hear shooting for 10-15 minutes after end of a battle. Actually I didn't encounter this problem in usual gameplay, but only when defending the Castle (I have More Attackers - Get Out of My Buildzone and More Enemies installed); about 15 settlers, 20 turrets, 20-25 enemies. I have a volume normalization option in Windows sound settings, but I tried to disable it and it didn't help. Maybe there are some ways to reduce/remove this lag?

I have a quite old CPU (i7-3770), but Fallout, Windows and saved games are on SSDs.