Sticky satinwood

[Cyclistbruce]

I repainted all the wood in the house with satinwood, having sanded down the original gloss.

All seemed to go ok, but the parts where we touch a lot, like the banister and kitchen door became really tacky and dirty. Even when we clean it they remain slightly tacky, but only where it's regularly touched.

I've ended up repainting the banister with gloss and this has stopped the stickiness. Any ideas why this might have happened? It was Leyland satinwood from Screwfix.