Front-Back Bandsaw Blade Wobble
I'm trying to find some help figuring out what's wrong with my bandsaw/blades. I have a Wen 3966T bandsaw, and with the original blade, it tracks perfectly. It's hard to find a 100.75" blade to fit it, so I've tried 100.5" and 101" blades. Grizzly had a closeout for some 1"x101" blades, and I'm trying to get those working - the other blade I've been using is a 100.5" wood slicer.
With either the Wood Slicer or the Grizzly blade, I cannot get rid of the front to back motion. If I clamp a piece of wood behind the blade with the table and rotate the blade, I'll get up to a 1mm gap between the blade and the wood that varies as I rotate (i.e. no gap to ~1mm). I get a similar but reduced effect with the wood slicer, and again, no front to back motion with the original blade.
I've watched a few videos on aligning bandsaws, including both of the Snodgrass videos (which are very helpful, except for this issue). I tensioned the blade and made sure the wheels were coplanar (they weren't due to varying tension), and then started to adjust them to try to minimize the issue. I tried to look for warp in the wheels and didn't notice any. I did notice the blade shifting on the wheels with this motion, particularly on the bottom wheel.
Is there something wrong about using a blade slightly off length, is this bandsaw a piece of junk, or is there something else I'm missing? Both the Grizzly and Wood Slicer cut well when new (the original blade did not...), but my concern is that the front to back motion will result in one part of the blade wearing out too fast (the Wood Slicer didn't last long at all).