multiple TGraphs in the same pad

Hello

initially I thought that this is too simple post, but ...

I have several graphs,

g1.Draw('AP')
g2.Draw('P')

now I can zoom both axis, everything is Ok.

g3.Draw('P')

it is not possible to zoom any more, why? This must be simple.

I tried TMultiGraph, it works, but it owns TGraphs and I get double delete problem because of Python memory management during reload. Why TMultiGraph must own its TGraphs?

Thanks,

       Margar