Yep I know that felling, but I was very lucky it slipped down a wall for about 6" and then, thank you god, dug in to my mat.
Its a bazaar feeling, when it happens. All went in slow motion.
Only do WFP now, will never do windows from ladders again as risk and consequences Versus financial gain make this an easy decision for me.
My mate who is still trad had a ladder slip the other week and it shook him up.
Some people say ladders are safe its the user who isn't. This in my opinion is total Botox, as many an experienced cleaner has come off.
Look at the design its totally basic with very little by way of safety measures.