To be more precise, tethers usually mean the wire type harness connected between tender and engine for steam. Also Diesel ABA types. The connector in the engine can have solder joints crack usually on the outside and this effects motor and some times power. PS-1 had sam affliction. Also the wire inside the harness from tender can break.
You seem to be talking about drawbars. Some can have the same solder cracking but it would be on one or both sides of the actual drawbar. So if you change it that was most likely culprit. But it can also be the harness from the tender or engine that plugs into the drawbar. Usually it is the engine side which is more restrictive. Tender has the swivel to keep pressure off tender harness.
Lastly the drawbar connection does need to be complete and firm. Partial insertion to tender can cause issues. G
