[bobbyh]

Thanks Chris! All my PHP scripts were OK (no syntax errors), but eliminating one more possible cause is always helpful.

It turns out that this Email Notifications plugin (https://bbpress.org/forums/topic/plugin-post-notification?replies=44) was causing the problem. After disabling that plugin, there are no “delays in posting” and there is never a 500 error. There must be a scaling problem with the plugin that started after the tables hit a certain size…

Thanks again for your help, Chris!