The suppressor you have consists of a capacitor and two RF chockes.
With age, the capacitor can (& do) go short circuit, often with an alarming bang. The role of the suppressor is to prevent the motor causing interference to radios and other audio equipment. Any mains powered motorised equipment such as a vaccum cleaner, electric power tools such as drills, sanders, routers etc, will have a suppressor, but usually only an Class X capacitor.
My only experience of sewing machine motors is when I used one with a foot controller in a Coil Winder I designed and made. It worked a treat till there was an almighty bang in the controller and I had to check that my foot was still intact. The foot controller was decades old, and the 'suppressor' was just a wax paper capacitor - not a Class X one. I replaced it with a Class X one and it's worked fine ever since.
You'd probably be fine with just a Class X capacitor, (which is what would have been fitted to more modern sewing machines), though 'vintage' suppressors such as yours, like the one at this link, are available on eBay. Described as 'tested and working' but by virtue of its age, it's anyone's guess for how long. That said, it's not a big outlay and international post is reasonable too:
https://www.ebay.co.uk/itm/352295172180?rmvSB=true
I've attached a quick sketch of the circuit of your suppressor as it most likely is, and the alternative option with just a Class X capacitor.
Hope that helps a bit.