fix

fix someone's wagon bring about someone's downfall; spoil someone's chances of success. US

1951Truman CapoteThe Grass Harp She said her brother would fix my wagon, which he did…I've still got a scar where he hit me.

get a fix on

1 determine the position of (an aircraft, ship, etc.) by visual or radio bearings or astronomical observation.

2 assess or determine the nature or facts of; obtain a clear understanding of. informal

❷2013Knowledge at Wharton It is difficult to get a fix on the number of taxis in India. Estimates vary anywhere from 500,000 to around one million.

if it ain't broke don't fix it: seebroke.