looking for advice to mitigate inner groove distortion

It sounds like you’re using one of the freebie alignment printouts?
Some of those are okay for alignment only after having set overhang.
How did you set overhang?

Overhang must be set accurately first. Otherwise if overhang is off it will cause your cartridge to be rotated too much one way or the other, which you may not notice until the inner grooves where it becomes more obvious.

My favorite for being fast, easy and accurate, is the MoFi Geo-Disc  https://www.mofi.com/product-p/mfslgd.htm which you will notice has a ridge line running A to B which must be aimed directly at the tone arm spindle vertical axis. Then you tape the platter so it doesn’t move while you’re tweaking alignment.

Even though you are not using the Geo-Disc nothing changes. The Stevenson you’re using must still be placed accurately in relation to the tone arm spindle, and both the gauge and the platter must be held stationary.

Try again with these tips and overhang set first and see how it goes.

https://www.analogplanet.com/content/uni-din-versus-l%C3%B6fgren-b-just-clarify according to Mikey's findings,  Stevenson alignment has the most distortion most of the time. Unless you're playing very long records you will experience the most distortion near the end of any album side.

Don’t forget to clean your stylus regularly too. A dirty stylus can seem okay outside the inner grooves.

Greg, the saving grace of Stevenson alignment is low distortion at inner grooves, compared to the two popular alternatives. One could argue about alignment all day but I strongly doubt that misalignment or Stevenson alignment can account for this problem. I’m now wondering whether motor is interacting with the cartridge as the two get closer to each other. To test this, with the platter spinning, pick up the tonearm and holding it above the platter but close as possible to it bring it over toward the spindle with volume control fully advanced.