See this link to downgrade the LG TV firmware. It’s not something I’ve ever done personally but it seems others have reported on Reddit that it works okay. These things though are entirely at your own risk:

https://github.com/reprodev/LGTV-Firmware-Downgrade

It might be worth voicing your concerns to LG, so they can fix the issue in a future firmware update. I’d be tempted to try a simple redownload/reapplication of that firmware, if possible, and I’d definitely try a reboot of the TV to force a reload of its OS. 

I have noticed some changes after LG’s latest update on my A1 OLED (03.40.70). I have a Beam Gen 2 and 2x Sonos One’s in a 5.0 set up through eARC with my TV audio output set to ‘Pass-Through’. Since the update I lost audio on BBC iPlayer and ITV Hub. In the Sonos app I now have ‘Unsupported TV Audio’. What I had to do was switch my audio output to ‘Auto’ so that it would auto switch to PCM audio I guess when needed. Just feel like I’m now not getting the best overall sound quality as I am now getting ‘PCM multi-channel’ on inputs where I used to get Dolby Digital. This is resolved by changing back to pass-through but I don’t really want to have to keep changing back and forth whenever I use certain built in apps. Also, if I leave Pass-through on but turn off eARC this resolves the issues but then leaves me without Dolby Atmos ability on other apps! All worked fine on Pass-through + eARC before update.

Perhaps related to this?