Below is a safety beacon from the CCPS from March 2019. It talks about not trusting valves for secure isolations for safety reasons. We have made an effort over the last few years to accomplish this by either replacing the valves with blinds or removing the line all together.
I can think of two examples off of the top of my head:
We need to continue to be vigilant in recognizing the potential for valves to leak. Continue to point out any locations where we have valves as secure isolation points, and we can get a blind installed instead.