Wilson Audio Sasha sound imbalance

A wavering center image in my experience has always been solved by more precise setup of speakers. Double and triple check your measurements as well as toe-in. The fact that it wavers only in a certain band strongly suggests to me it isn't a balance issue.

I mean no disrespect but if you read my posts earlier I have advised that initially I tested swapping the WATTs and the image moved to the opposite side.

No two speakers are identical. You want to fix it? Get a DSP preamp like the Trinnov Amethyst.  You can analyze individual speakers and give them the same response curve. 

The Trinnov stuff looks interesting. The Amethyst is a little pricy for my blood, but the ST2 Hi fi looks like it has a good bit of the performance and a more manageable (for me) price.

Have you called Wilson? It’s not hard? They will help you. If you swapped the speakers and your issue moved with the speakers, one of them has an issue. A driver on its way out, a connection problem somewhere, or perhaps an issue with a crossover. If you haven’t tried to change out the resistors, try that. The experiment you tried with a mid vs tweeter and centering the image won’t work. The easiest way to test a tweeter is simply cover it with your hand standing in front of the speaker then uncover it. You will notice the difference, it will be night and day. That doesn’t mean the signal getting to the tweeter is correct though, or that the tweeter is 100%. Same goes for the mids.

Have you done anything with your source? In the troubleshooting you need to check cables, and any other connection, the problem may have nothing to do with the speakers.