"I have read if I run a length of insulated wire (any gauge) between the tracks and connect the wire to a ground plug, the problem may go away. Do I understand this correct?"
Where did you read that? The answer is that at no time should any part of the track circuit be connected to ground. That is unsafe and illegal.
If you have trains that slow down and stop at locations that are furthest from your power connections, you need to run jumpers (both center- and outside-rail) using minimum 16 gauge copper wire from the existing power connections to points at the opposite side of the ovals, and several points in between. Hot to hot, and return to return. (Visualize using jumper cables between two automobiles.)
