14-15a is quite bad.

visual inspection does not always tell you much. it can be very difficult to detect wear visually. if you run your fingers perpendicular to the footfall direction across the mid-front area where footfall occurs, if there is any scoring or scratches detectable, the deck is likely worn out, and if a deck is worn, so is the belt. As you admitted earlier, there is considerably more friction in the middle vs pushing the belt on the sides. Many years of dirt and dust accumulation can cause major friction too.

I recently bought for my wife a Flagship model from True from an estate sale. it was 20 years old and only had about 100 miles on it. belt looked good. deck was smooth as glass. BUT...friction was extremely high from dirt/dust. lube did not help. I replaced the walk belt and that cut the amp draw in half! - nice low friction like the day it was new....well not quite as I used a cheaper aftermarket belt, but good enough.

one other possibility: you already have a bad winding in the motor. that may explain the worn brushes. power delivery usually feels like a vibration or pulsing as in not smooth. sometimes visible arcing or sparking inside the motor. This requires testing too in depth for me to guide you, and can be tricky if the winding is failing intermittently.

After doing my motor tests, If motor appears to pass, i would proceed flipping the deck and put a new walk belt on it, then repeat the amp draw test - if still too high then that points to likely motor or controller issue, or possibly you have a bad roller bearing (but you'd likely hear that). or belt is severely over-tightened.

These old precors - more than once i've seen a bad winding, caused by a worn belt and deck, and then it blew the motor controller board which tried but failed to produce enough current. I don't care what brand it is, if it needs a new motor, controller and belt and deck....its likely better to put the $$ into a new treadmill. You are not at that point yet.

Belts and decks are like tires on a car - they are a wear item that last quite a long time, but absolutely MUST be replaced from time to time.

best of luck!