for definition;
The "breech" is the big fat part screwed into the end of barrel that holds the nipple and has a "hook" on the end.( TC used a "hooked snail breech")(nice! very reliable).
The "tang", is the metal part installed in the wood stock that receives the hook part of the breech.
If there is movement between these pieces when the barrel is installed, you'll get one heck of a "kick" when shooting.
Now, too determine if there is wear at the point of tang/ breech,,and not worn or miss-alignment of the tang to stock, simply remove the tang and hand fit it too the breech hook while both parts are out of the stock. You'll then be able to see which part, if either is worn. When the face of the tang is against the breech there should be no movement. It is a T/C so it has a "Lifetime" warranty.
However, sometimes a small shim of some sort under thefront screw of the tang as it's installed in the stock can help bring it back in place just for the season.
P.S. don't strip them wood screws holding the tang in the stock, a little bar soap rubbed on them threads helps