This topic is from 2018, but...
One cause of apparent uneven chain wear is that the outer links don't wear at all, so if you measure such that there's one more inner link than outer, you'll get more wear than if you measure one more outer than inner.
You can avoid this by always measuring an even number of links. You'd hope that all commercial wear gauges did so, but using a ruler or a vernier caliper might not.
Yes, I realized it was an old thread but I understand it's preferred to continue it rather than start another thread on the same subject.
Yesterday, after finding the uneven wear I searched 'Uneven chain wear' and came across a few things, one of them being the 2018 thread. Elsewhere I read that the way the teeth are ground on the side can cause it. I don't see why that is. I can't find that website which explained it, now.
I just now went and checked the chain, again, using the Park tool and a Pedro's checker. Pedro's indicates it's okay but I didn't check it in several places. The Park tool has two pins, one of which goes between the inner plates, and the other pin between the outer plates. In the past I haven't checked it in more than one place, which is why it surprised me, yesterday.
The sprockets look good. Anyway, I've ordered a new chain. Even if some parts of the chain are good, it's still not a good chain.
Incidentally, I replaced the chain on my cruiser about a year ago. I got the new chain from a LBS, and it was in a blue Shimano pack. After riding a 100 miles I did the usual service and found the chain was worn out. The bike shop has been in business for at least 40 years and I don't believe they'd sell me a used chain, so I tend to think that somebody had bought a new chain, put it on their bike, put the old chain in the blue Shimano pack and took it back for a refund. That's pretty low. I didn't tell the bike shop about it.