Here is the extent of what I know about that...……"not good at all."

Glad I didn't do it.

backlash, somebody needs to put down the baitcaster and go back to the snoopy rod

Does any/all of the equipment yal send down have cameras on it?

Wireline can run a camera, since it’s electric. That usually means something ain’t right, and the usual logging tools or impression block isn’t telling them exactly what they want to know.

Hell of a backlash fished up right there. Hopefully was able to pull the tubing with no downhole pump damage when tools were dropped.

What is the purpose of the valve that caused the issue? Isn't there a way to lockout/tagout while the slickline is down the hole? Or, is it an emergency "stop" for whatever other bad thing might happen? bear64 and I are in the same boat, facinated but know nothing but what I read here.

That valve shuts the well in. It could have been LOTO, with a chain, since those valves are typically gate valves. That’s not typically done. You want access to that valve for purposes of well control. In that situation, it would be used as a last resort. It’s understood (or supposed to be) that you don’t operate those valves unless you’re 100% sure of what you’re doing, especially when working on the well. People are human, though.

This has nothing to do with the OP story, other than mistakes can happen, and be costly.

While in high school and college I worked for a rental/service company in SE OK. We rented all kinds of tools including blowout preventers (BOP) and part of my job was to service the tools when they came off of rental. When we serviced the BOPs, we cleaned, replaced the dogs, and tested to about 4000 psi. To test, we bolted to a base, then placed a section of pipe in the dogs with a bull plug on the down end and cranked the dogs down tight. We then filled the BOP with water and hooked to an air compressor to build to the test psi. One day another guy was testing a BOP, but placed the bull plug end of the pipe UP - meaning as the pressure built, it built inside of the pipe. As it approached max psi, the dogs failed and the pipe became a missile. It launched up through the roof of the building, across the parking lot, and landed on a parked car. Everyone in the shop thought there had been a gas explosion. The new guy was unhurt, but soaking wet and very confused. He was let go that same day - he could've easily killed himself of someone walking across the parking lot.

When I started reading that, I knew exactly where it was going. We had a guy do the same thing with wireline rams. It just left a much smaller hole in our roof than those pipe rams.