People will finish updating when Photos is in the background

I came here to look for help with this issue as well. As background, my library has over 60,000 items in it. I had done various face tagging in my various devices before syncing came with High Sierra, so there has been a lot of duplicate faces and merging that I've had to do since upgrading. With my library being so big, I expect things to take a while. But it now appears to be stuck. I have multiple iOS devices set to "Optimize Storage" but my 2017 MBP is set to "Download Originals." Some observations:

• Each of my iOS devices show different numbers of "Photos Scanned" and "remaining photos." Occasionally the numbers will change, but only by small amounts (like 3-20).
• If I add/edit a face tag on one device, SOMETIMES the changes appear on the other devices. I say sometimes because occasionally, after adding or editing existing tags, I will come back later and see that all my edits have been reverted. It seems to happen with specific people/faces. Not sure if this issue is related.

To debug, I've checked Console app and filtered on "photoanalysis" and see that it tries running but often bails due to "thermalLevel >= 1". It decides not to proceed:

501:com.apple.photoanalysisd.backgroundanalysis:FA7A10:[

{name: ThermalPolicy, policyWeight: 1.000, response: {Decision: Must Not Proceed, Score: 0.00, Rationale: [{thermalLevel >= 1}]}}

], FinalDecision: Must Not Proceed}

So I assumed the CPU was running too hot, which forced photoanalysis to bail. So I unplugged my 5K monitor (which makes everything run HOT HOT HOT!) and closed all apps to go minimal in the hopes that it would allow photoanalysis to proceed. Occasionally I will see it proceed:

501:com.apple.photoanalysisd.backgroundanalysis:FA7A10:[

{name: DeviceActivityPolicy, policyWeight: 2.000, response: {Decision: Can Proceed, Score: 0.85}}

] sumScores:31.710000, denominator:32.010000, FinalDecision: Can Proceed FinalScore: 0.990628}

Even when it does run, it doesn't seem to do much. It runs for like 5-10 seconds and spews a bunch of debug lines into the Console, then appears to finish. But there is no indication in Photos.app of any progress at all. I've left my machine on for days/weeks, plugged into power, but nothing appears to be moving forward. Anyway, just wanted to "me too" here and see if everyone else could peek into their Console.app and see if they find anything interesting in there?