The latest iOS version 11.2.6 is making some users’ AirPods stream in mono, instead of stereo. That is, the same audio channel is coming out of both AirPods. If you only ever listen to podcasts, you may not have noticed this as most podcasts are recorded in mono, but if you listen to music it might be driving you nuts.
The update may also be screwing with the AirPods’ tap controls.
Either way, the fix is easy.