ABS waving, bubling, whatever

Hi everyone,
does anyone know what causing this ? It looks like bubling or waving. Print head a little bit vibrated on these places and there were little tooth. I printed whole day and everything was fine. But last print looks like this: picture in attachment.

I checked all, diameter, temperature, nozzle possible clogging - was clean, it was the same setting.

So any idea ?

moisture in filament, loose belts or other backlash in drive, hotend moves freely.
Those are the most likely ones.