I become very sad when people say they "fix" their car but it keeps "breaking" especially when it's a mechanic who is "fixing" their car. They moan about the cars lack of reliability and ***** about the mounting costs at their "trusted" mechanic.

While it is possible to experience failure of a new stock or refinished replacement part; most of the time if someone is paying a mechanic to "fix" something that is constantly "broken" like say... A front suspension rebuild that keeps eating tires they are getting bilked. There are a finite number of components that can affect each fault, like worn tires. Once someone goes through that finite number of components and systems to replace the defective ones they then set everything to "spec" and see if the problem (worn tires) is corrected.

Occasionally an obscure part will be overlooked, or a good new part can unexpectedly fail, or the mechanic makes a mistake. It happens to the best of us. The fault (tire wear) is then reproduced. The car reenters the shop and they search until they locate the cause of the fault. Once the system is repaired the car is again released to the owner. Keep in mind when I use the word "system" (front suspension) that system can be made up of a LOT of parts. Hundreds of them. But one by one you can check them out.

Obviously it's never a smart financial decision to take a transmission completely apart because it takes too long to shift into reverse, or if it always slips on a 3-2 upshift. This is when owners usually take a dramatic step and replace the entire system (transmission) with a "good" used unit rather than rebuild the original. Often, this works out fine. Occasionally some new running issues are uncovered when the new unit is in place. Usually this can be attributed to other "systems" having been adjusted to meet the performance of the old failing part. With something like an entire transmission, there are a few adjustments that need to be made before the unit will work as intended.

Something such as a front suspension though on an old car can be a lengthy battle. The point is every battle eventually. The design of these cars is very sound it's the decades of poor maintenance that causes frustration.

If something is broken, and right after it's "fixed" it once again breaks, 99.99975% of the time it's because it wasn't fixed properly the first time. the other 0.00025% of the time it's because the part you thought was good wasn't in fact good. Even with new a stock.