First off, are you using analogue or DCC? I'd assume analogue, but recently so many posts have been in the wrong section!
Second - you say you have a gradient, on a fairly small layout. Have you checked if your locomotives will even go up a climb that steep? Very few will, and certainly not when towing much of a train behind them!
Third, without being able to see your track plan, we can't really help a lot with your main question about possible problems. If you post a drawing of all the track, or a photo, then we can take this further.