Some engineers home built kernel which could literally contain whatever the hell problems
for a bit longer, I can't help thinking if the actual background is that the build environment for Pixel 4a simply doesn't exist anymore, so they ended up building on a dev PC, possibly one that has been mothballed since Pixel 4a development stopped. Definitely not a good sign, but it could explain why.
Assuming that Google isn't just doing this for fun, it might be a good idea to look into your battery. This little post shows a simple way to determine if you (could?) have a faulty battery: https://ancillary-proxy.atarimworker.io?url=https%3A%2F%2Fwww.reddit.com%2Fr%2FPixel...
According to the findings by Hector Martin, I have a faulty battery, even though it could easily hold a charge for a few days with my usage prior to the update. Now it's good for about a day.
I THINK MAN INVENTED THE CAR by instinct. -- Jack Handley, The New Mexican, 1988.