So, this is a problem I have been experiencing for just under a year and have just figured out what it has been for me. I found it by looking at cgslav's post.

For me, it was a simple matter of the location being at a negative value. It seems that when you move the light around in blender it gives unpredictable values for metric based location... which makes sense since it's a program based on scale and non mm :/

So, this is a problem I have been experiencing for just under a year and have just figured out what it has been for me. I found it by looking at cgslav's post.

For me, it was a simple matter of the location being at a negative value.

I found this by pressing N to open the side menu and saw that my light was 120 metres below my object, even though it didn't look that way in the viewport.

It seems that when you move the light around in blender on multiple axis it gives unpredictable values for metric based location... which makes sense since it's a program based on scale and not metres :/