Not always but certainly more often than not. When I create a mesh light and then select pick mesh, after clicking my object it creates the light but it moves it to a random point in space. It doesn’t maintain the original objects position. Some times it does, some times it depends on whether I have selected “replace mesh with light”.
I had this before. Try to reset transformations and put a reset xform on that piece of geometry you try to create your light from. Worked for me back then.
Hmm reset Xform was grayed out suggesting that it doesn’t need it but still it places the light incorrectly. Even if I put in the XYZ absolute coordinates from before it was made into a mesh lights it is still in the wrong location.