Heel and toe of razor gets sharp, but not the middle.

Think of honing a smiling blade as a knife with a slightly curved edge. Which is what such a razor actually is.

This was posted on bnb also. My diagnosis there was the same as was posted here early on in the thread - the spine is slightly crooked, so honing the blade results in one side hitting heavier at heel and toe but light in the middle and the other side hitting heavier in the middle but lighter at heel and toe. End result, the bevel has not yet been properly set in the middle of the blade on the side that hits light in the middle.

So far, nobody has mentioned the stones. I would flatten a bevel setter (1K) using the grid method to make sure it is flat then reset the bevel and watch the process with your loupe. This will confirm if it is a blade problem. If the bevel is incorrect, not set properly, the higher grit stones will not solve the issue.

Also, sometimes a 2nd layer of tape can be like magic to a problem edge. Try that after you've tried everything else and see if it helps.

It's not the stones IMO. The pattern would almost certainly be very near the same on both sides if that were the case. Aside from this, yes the importance of stone flattening was already mentioned earlier or maybe at bnb, don't remember, and the OP mentioned he would "pencil grid and lap again," so I am pretty sure he has that down.

the pattern of wear described by you is consistent with a spine that is slightly bent to the side the heel and toe get sharp. Use a rueler to check if the spine is straight on both sides.

I think you were correct with the twisted spine diagnosis. It took some time and electrical tape, but it eventually got sharp the entire length of the blade. Thanks for the help/advice guys!

Glad it worked out....it happens because there is tension in the steel matrix...possibly due to bad heat treatment ... bad quench or insufficient tempering...
I have seen this am many blades....when they leave the factory they are streight but in lots of years as is the case of old blades the tenssion tends to even out and bends the blade slightly....I'm sure we' all seen cracked blades that were not cracked mecanicaly...or spines rhat are not streight....the fact is many blades have geometrical defects hidden to the eye...they were made by humans not by machines...

This is pretty common really, and isn't necessarily bad heat treatment. Often when steel is quenched it will distort if there's any residual stress. The razor makers of course need the spine to be reasonably straight, so they straighten the razors as close as possible then grind them. Over time, the steel will tend toward relaxing back to the position of lowest residual stress, so if the original bend was significant but was straightened, it can come back gradually over several years.

One way to almost completely eliminate this issue is to perform a stress relief thermal treatment before heat treating and then do not straighten if the steel goes out of whack, but rather grind it until you get where you need to be dimensionally and straightness wise, but I don't think many would ever do this as it adds a good amount of time and therefore cost to the finished product.

So instead they go the route that they do, and now and then you get a stinker... but you almost never know that when the razor is new so it doesn't hurt sales.