Yeah, I'm impressed with the 756 and the other 600 series (even though I feel the lever design is more finicky and time consuming to work on thus requiring more patience). I just started working on another, my 5th (plus a Futura 900 though isn't a T&S) that's a 758 with the most frustrating confusing experience of the timing going out of wack. Eventually, I found the YT video "
Singer 758 Touch & Sew rebuild Incl/timing belt & gears.Worth it if you love your T&Sew (video 158)" by Randy Your Sewing Machine Man that led me in the right direction being the belt as the causing once I shined a light on and inspected more in detail.
Then searching around I saw the method Mikegenwood and another user used and am thinking will give that a more thorough review and try. Possibly using the 3M PR# (not sure which number yet) Scotch-Weld adhesive as a test if I can get some free samples maybe. :-).