This wooden door frame (see photo below) was painted high-gloss white a month or two ago. Using cheap paint and a cheap paint brush. The surface was superficially sanded (previously painted a number of times before), but cleaned quite well.
If I remember correctly, the ambient temperature would have been around 11-15C/50-60F.
Unless you pay attention it's not super obvious, but when you look you can see this effect, and you can very definitely feel the ridges when you go over them with your finger nails. I took the picture while shining a harsh LED light on it to make it more visible.
What could be the reason for this paint effect? I can think of paint quality, brush quality or not enough prep, incorrect application (although I don't regularly pain, I have painted quite a bit, and never seen the before). Or something else. Or perhaps it's impossible to tell from just a picture.
Could this be buffed out with a very high grit sandpaper or abrasive gel? Without losing the gloss.