The site is behind a proxy, yes. apache serves the client site redirecting 80 to 443 and serving SSL for the site then proxying to Nginx for postorius/hyperkitty at 8080. I've also tried going straight to 8080 bypassing the proxy internally using localhost or loopback to the same end result.
The log is mostly these three errors repeatedly with the same above wall of html between them, some of them end with (404) after the last html tag indicating url not found and browsing to them gives the same custom 404 page for postorius.
Jul 15 12:37:08 2021 (471314) HyperKitty failure on http://lists.client.org/hyperkitty/api/mailman/archive: Jul 15 12:37:08 2021 (471314) Traceback (most recent call last): File "/opt/mailman/venv/lib64/python3.6/site-packages/mailman_hyperkitty/__init__.py", line 154, in _archive_message url = self._send_message(mlist, msg) File "/opt/mailman/venv/lib64/python3.6/site-packages/mailman_hyperkitty/__init__.py", line 210, in _send_message raise ValueError(result.text) ValueError: Jul 15 12:37:08 2021 (471314) Exception in the HyperKitty archiver:
I was able to find (about 5000 lines up in the log for a single post attempt... it's a bit excessive to print the html response every error) this when I dug through instead of tailing the last 500 lines.
[15/Jul/2021:12:37:06 -0700] "GET /3.1/addresses/sarah.h@email HTTP/1.1" 200 380 "-" "GNU Mailman REST client v3.3.2"
and at the start of the block:
[15/Jul/2021:12:37:03 -0700] "GET /3.1/lists/admin.lists.client.org/member/sarah.%40email HTTP/1.1" 200 516 "-" "GNU Mailman REST client v3.3.2" Jul 15 12:37:05 2021 (471317) ACCEPT: <162637782380.3116.619498070458942231@sysname>