Ford ranger edge brake pedal going to floor on stop

It's not normal , it IS dangerous , don't drive the vehicle till you get it fixed .

It is not normal, from what you are describing the braking system is in dire need of repair and they could fail at any time. You need help ASAP.

Have taken it to the shop, says can't find anything. Master cyl apparently ok. Any ideas on what the problem might be? When driving the brakes seem fine when slowing down, the problem is when coming to complete stop. Where do I start?

There are lots of articles online on what to do if you search. But you want to check the fluid level first, if low, then check for leaks around all four wheels and all brake lines and hoses and replace. If the brake fluid level if full, then you have a master cylinder seal issue and it has to be replaced. If your mechanic said everything is fine, you need to find another mechanic you can trust and that is concerned for your safety.

Sounds like the shop couldn’t be bothered with doing some actual diagnostics. So I’m going to assume that you have tried bleeding the brakes with the key turned on. I ran into a few in my time that I had to reverse bleed the entire system to get the air out. So if bleeding the normal way doesn’t work then you might see if you can find a shop that can do it. If your still having problem then it might be the ABS bleeding off pressure, could be a bad EBCM or the RABS unit itself. Hope this helps.