"Remember me" login not working, specifically on phpbb.com/community

Specifically within the last week or ten days, suddenly when I navigate through https://www.phpbb.com/community/ forums, the "Remember Me" and/or fact that I'm already logged in for the current browser session just fails over and over again.

Meaning, I shutdown everything and then open a new clean browser session, and navigate to https://www.phpbb.com/community/. I'm not already logged on, which is odd since I selected "Remember me" during the last login I performed, but whatever. I can login successfully using my account credentials, and select "Remember me" for the current login again.

That gets me to the forum summary page, and it's showing the correct read/unread information because I'm now logged in. But if I click on one of the forums, like 3.2.x support, the forum comes up, but "I'm in logged-out state again." Meaning the "Login" link is back, and if I want to see read/unread flagging, I have to login yet again. And the login works; but I had to do it again.

The bad part comes when I'm trying to reply. Simply reading a specific message may again return me to the logged-out state, and I have to login yet again. The real problem is that when I go to submit a reply, and instead of submitting (or even previewing), I'm asked to login again, and the message I was working on is lost once I successfully provide credentials.  I have to keep my message in cut-n-paste, and retry multiple times before it just happens to magically work by posting rather than prompting me for login again.

Yep. I know what you're thinking. Here is what hasn't solved the problem:

• Using the phpBB-provided link "Delete cookies", and then shutting down all browser sessions and trying again.

• Using the phpBB-provided explicit "Logout" link, then "Delete cookies", then shutting down all browser sessions and trying again.

• Using the Google Chrome 69.0.3497.100 (Official Build) (64-bit) (Windows 10) option to delete all cookies for the site, then shutting down all browser sessions and trying again.

• Using Microsoft Edge 42.17134.1.0, which I've never used on phpBB.com before to have any existing cookies or history, but I still see the same behavior in that browser too.

• Remote Desktop into a machine at work, which is using a different ISP, different installation of Chrome, different anti-virus, etc., but I still see the same behavior on that machine in that browser, too.

• Time on all tested machines is in sync with NIST NTP sources.

• Changing my profile time zone from "America/Belize" (which had UTC-6 I was looking for) to "America/Chicago" (which has UTC-6, but probably more accurate DST).  And then used "Delete cookies", and then deleted cookies from Chrome as well, and then closed all browser sessions and trying again.

• All tested machines have been rebooted multiple times as part of normal use, but the issue continues to occur.

The "Remember me" option for MY OWN phpBB site (3.2.2) remains working as expected. The "Remember me" for other third-party phpBB sites I frequent remain working as expected. Only the https://www.phpbb.com/community/ site is presenting me with this issue right now.

So that makes me want to think, did phpBB.com/community change something in cookie settings, or maybe the update to 3.2.3? But if that were the case, I would be expecting the issue to affect multiple people and be a topic of discussion. Maybe I'm just missing it.

Otherwise I'm left to assume it's somehow unique to my specific phpBB.com/community login account, in a way that allows the issue to persist across multiple browser vendors, multiple cookie re-creations, and multiple machines.

I guess if no one else is having the issue, the next step is for me to try abandoning this account and creating a new one, to see whether the results are different.

If anyone knows how to debug the phpBB cookie usage that would be appreciated too, but it will have to be "from my end" since I'm not seeing this issue on any board except https://www.phpbb.com/community/, and I won't have admin access to the server for any troubleshooting steps.