worthy or false favourites of certain trainers

Treading very carefully here and choosing my words very carefully but certain trainers I bet on seem to let me down when I back their horses which start favourite in a race. Is it possible the bookies mark them up wrongly as favourites due to the trainer name and reputation?
My main question is this. What are the usual success rates of trainers as a percentage when their horses start favourite as opposed to when they don't?
(or is this a normal frustration of punters who seem to feel they have no success with certain trainers?)
I will give the two main specific "spoiler" trainers in my experience if this is permissible without suggesting any allegations of wrong-doing on their part. I just want to know when I have more success of backing their winners.

Prices are heavily influenced by who the trainers are. You only need to look at maidens with horse that have never run before. Those at the front of the betting will be well-known trainers. Gallop reports also play apart in this type of race. These horses will often run worse than those that already have form.

For all other races, big name trainers and jockeys do lower the price of a fav, and this can make the price false, but not by a large margin. This is why it is slightly easier to profit from smaller yards, and unknown jockeys, as they often go off at bigger prices.

lets just say it almost feels personal with one trainer in particular - when they have a well touted and tipped up fave it normally loses as one did at the weekend yet when I leave well alone it normally pops up at a decent price! (mick)