ECS NewGRF: why do these station ratings drop?

For whatever reason, ratings for oil in both Transfer and Valley stations drop to Atrocious and the amount of oil I get continues dropping. There are enough trains and truck to have one always loading.

I'm using ECS all vectors and Expert industries NewGRFs.

Why do oil ratings drop to atrocious even with one vehicle permanently loading?

Solution 1:

By starting new games disabling single NewGRF I found out the behaviour in my game was caused by clashing ECS basic and ECS basic II - any one of them didn't cause trouble, however having them both crashed industries rating systems.

So after starting new game go to NewGRF options and look, if there are titles in red. Those mean that there are errors, read them and start a new game with those resolved.