Lightmaps appear all white

When I change my viewport to show the baked lightmap it appears all white.
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But in normal viewmode the lightmaps are there and look correct:

I’m trying to debug something else, but the white lightmaps have me puzzled…

There should be an exposure slider somewhere on the scene view when viewing lightmaps. You might have the exposure set too high. It looks like this on newer Unity, forgot exactly where it is on older Unity
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