lambrightkevin
Hello & Welcome to the Forum!

My first suggestion is with the transformer on 100%, take a voltage meter and check each piece of track to see how much power available.
If continuous power reading is available 18 volts then check your locomotive.
IF not, check the pins and connection slots  on each piece of track and clean them bright..

If that isn't a fix, then you need to clean your wheels and pickups on your locomotive & lubricate the rollers.
I use smoke fluid to clean the wheels and rollers with. Alcohol works and other foks have their favorites.

Happy Rails!
dave