I really think some of these issues are tied to how vBulletin 3 parses threads and posts. In fact I know some of them are, as described
here.
I seriously dont think the designers ever anticipated threads with 30,000 posts. The fact that Hybrid view is not paginated is proof of this. There is literally no limit to the amount of posts it will try to process while using that thread view option, which means it eventually hits the caps we have in place on resources a single process can use. Those limits are there to help prevent problems, and to prevent faulty code from getting the server stuck in a loop from which it never recovers.
As the site gets bigger, we will run into these things more often. We have taken a few steps to try and nail things down specifically, and when the site is running properly it runs great. When one of these threads posts/threads gets stuck, it basically has to kill the process. We have a max of 180 or so cgi processes running at once, so losing one process shouldnt be a big deal though it will throw an error for the person using it at the time.
If that process happens to be the parent process it may kill the connection for 20 people when that process gets restarted, or those 20 people may have a long page load time as there is a 30 second limit built in.
The problem is that this is not consistent, its been really hard to figure out exactly what person was viewing which section of the forum when an error gets thrown. To limit that a bit I have closed several threads around or over 10,000 posts, and reconfigured the way that processes spawn and get closed on the server side.
Whenever we make changes, I have to wait at least 24 hours so I can view the logs and check errors over a long period of time.
I am glad you guys are still reporting issues, as it gives me a time frame I can look in the logs for.
A few other things you can do:
Tell me which thread you were trying to view. If you were simply looking at the main forum or really any section then it wont really help, but if you consistently have problems with a single thread then I need to know which one.
Set your Thread Display Mode to one of the Linear settings. Most people are on this already. I could force people to use it and remove the other options, but we havent gone that route yet.
Report large threads, 10,000 or so posts. I have no idea how many we have, but we need to close them and open new ones.