My tr-944 behaves somewhat similar except it gives brief flash of all densities. So I can use it, but I have look the reading carefully so that I don't miss it.
I have also zero the densitometer after taking reading, otherwise the next reading will be relative to previous.

As your's densitometer also flashes reading quickly (except showing only high densities), I wonder if this is some common issue.

But why only densities near 3.0, strange.