Doesn't sound like a paint problem, it is probably the corners were just not filled flush when the original mud work was done. 50's- i assume plaster walls, not sheetrock?
BtW- multiple coats of primer does not do priming better. Primers solve problems, maybe in your case there was some dirt issues that it could help with, but paint covers and changes colors better.
I think you have what you have- to fix it might mean reskimming/ filling those corners, then retexturing- a very big job.
If you can get a pic of what you mean and put it up that might help.
BtW- multiple coats of primer does not do priming better. Primers solve problems, maybe in your case there was some dirt issues that it could help with, but paint covers and changes colors better.
I think you have what you have- to fix it might mean reskimming/ filling those corners, then retexturing- a very big job.
If you can get a pic of what you mean and put it up that might help.