Gauges won't snap into place

I’m trying to add some gauges to my PV system monitoring dashboard. I’m having an issue where the new gauge won’t snap to the correct place in the dashboard. There is visibly room but Grafana won’t place the gauge where I drag it but offers to slip it into a different row, see the examples here.

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My guess is that there is something occupying those grid positions in the second and third line which Grafana avoids. How can I see what it is? There is one panel to the right, but moving that won’t help. In fact, it looks like the whole bottom right corner of the dashboard is off limits and nothing can be dragged there.