Question: Airport Express Airplay slightly out of sync
I have an Airport Express connected to my stereo. Starting a few weeks ago, I noticed that the AirPlay audio suddenly is slightly out of sync with videos. Please note, I don't mean the 2sec delay that would be observed when the Airplay delay correction isn't working at all: It is working, but it is off target by about a quarter second. This problem came out of nowhere and video was perfectly in sync before.
I determined using VLC, where the delay correction must always be made completely manually for some reason, that the problem must be somewhere in the Airport's processing. The total delay to the audio out is about 2250 ms, and I read somewhere that it should be exactly 2000 ms. So that would explain what's happening. But how can I fix it? It's not in my stereo, as the problem persists when I plug headphones into the Airport.
The problem happens both with my iPhone and my Mac (latest OS everywhere including the Airport express). I tried resetting the Airport Express already to no avail.
Thanks for any pointers
iPhone SE, iOS 11.1