Rebuild content timeout and no async log messages

I have a problem with the “Rebuild content” functionality.

If I do a “Rebuild content”, the log doesn’t update async and the requests to the connector stay “pending”. After a while the connector request times out and the async requests keep going on forever. See

It seems to work, when I limit the resources to be rebuild (manually in the rebuild processor). But the log still doesn’t behave as it used to. Looks like it gets filled with the response after the success message is sent and not async. See

No errors in any log (MODX, PHP, MySQL).

Latest Chrome, Firefox, Safari.

MODX 2.7.1 advanced
ContentBlocks 1.8.12
PHP 7.2 and 7.3
MySQL 5.5.5 and 5.7.26
Apache and NGINX

Looks like I found the problem: session_handler_class.

We are using the standard PHP session management and not the default MODX database managed sessions (“modSessionHandler”).

So could it be a problem with a locked session?