I had a bike with a problem like this, I pulled the BB apart for service and noted that the bearing path traced in the cups was an ellipse, on both sides! The BB shell was not square and the threads were aligned to the off edges of the BB! Scary. And this was on a "custom" British Lightweight frame... An hour with a Campagnolo tool kit and some Sturmey Archer cog washers to take up the loss of BB material required to set things right solved the problem. Only other choice would be to use a Phil Wood cartridge BB, the threaded rings are short and can be misaligned to the cartridge a bit. Not a cheap fix, but we were not talking cost.

Or look for a Mavic cartridge BB, facing still required, but the lock rings seat into a chamfer that needs to be cut into the BB shell. A good choice for less than great quality frame work.