Adding a panel to a dashboard multiple times is broken.

Steps to reproduce:

• Create a new dashboard, I used 2 columns, half&half
• Add existing panel W123 (arbitrary) to the left column
• Add existing panel to the right column --> choose W123 again --> "wow this is allowed and actually works"
• Remove first instance of W123
  • Second instance of W123 is also gone --> ":-( but I knew I was playing with fire"
• "OK, I must not do that. Let's move on and just use W123 just once as it is intended."
• Add an instance of W123
  • Second instance of W123 appears out of nowhere ... "ooOOooOO I broke it!!!"

I can now toggle between zero and two instances of the panel :(
But I can no longer really use W123 on my dashboard and need to start with a new, un-broken dashboard if I want W123 on my dashboard.

Dashboards should not break like that.