You just chew the thread to pieces and the jack collapses on you!

Don't ever trust an old scissor jack, when the thread lets go, it comes down
in a hurry.

I know from experience getting caught between the garage wall and the 1970
tiny little Corolla and that was being jacked up with a V8 Ford scissor
jack. It stripped the threads out of the nut! And almost stripped my
nuts!!!!!!

Hope this helps,
Peter