Does this happen near shore line or harbor areas or out in the open sea? 256 should be OK to be at and not run into "slow stops of TC" like you're describing but if your PC is slower it still might drop to 1x slowly.
My main problem is that I'm dropping to 1x but NOT hearing the "ship sighted" or "contact heard" messages and I wish I knew why. It's obviously some mod conflict since for a while it happened.
For your issue though, 256 should be a "safe" TC to be at and not miss ships.
