That sounds like you haven't subscribed or activated the Trailer Variation Loader mod listed in required items. Each trailer contains 9 submeshes for different cargo types (goods, animal products, grain, logs, ore, liquid, etc.). The mod will switch off all but one of them to reflect what kind of cargo it's carrying. without it they will all stay on.

any ideas why trailers are flashing like there's more than 1 textur/trailer?

Nice. Looks great cant wait to incorporate this into my current map