My pool does not leak like it did last year after the new liner was installed :-D.
Last year it lost a noticeable amount of water every night, and I was chasing the leak even though the bottom had collapsed

.
When we dropped the liner and rolled it up in the shallow end recently, the source of the leak was found. When the liner was replaced last year, the old liner was cut away around the returns, the old liner was left in place, with the new liner installed over the old one. This can be seen in the second picture of this thread.
While the pool guys were fixing my bottom, I fabricated two sheet aluminum patches to repair the corroded walls where the returns attach. Because the earth and return lines have settled, the return flange's are no longer perpendicular to the walls. I fabricated two custom gaskets to fit the misalignment, filling the gap between the return flanges (that have settled) and the newly fabricated wall patches. I took 1/2" rubber and sanded it with my belt sander, creating a tapered gasket that is 1/8" on the bottom and 3/8" on the top. After fine tuning the gaskets to fit slightly thicker to allow for crush, I sealed the back sides of the the patches and gaskets to the flanges and walls, and then attached everything with the four return plate screws, using a longer screw on the top due to the thicker gasket. After an overnight cure with everything bonded in place, I used 16 SS screws to attach each patch's to the aluminum walls, then I remove the return plates and four screws, before rehanging the liner.
My pool guys like the repairs, and everything seems to be working without leaks, so I am happy!
Pictures to follow in case anyone else has an old pool with corroded walls where the returns attach.