I observe a strange behaviour when dividing 2D histograms (TH2D).
I first fill a few TH2Ds with ~10^5 entries, I divide two of them and then I plot some projection with errors. I always get by few orders of magnitude too high errors.

I tried histo->Sumw2() at many places (after creation. before filling, before dividing), but with no effect. I use version 3.10/02 .

Also Scaling behaves weirdly - if I histo2d->Scale(X), relative errors reduce by sqrt(X) - i guess they should not change while scaling…

with best regards and wishing good time developing
0ndrej