So you clearly have some DB problems (out of memory there and lost connections). Whether that accounts for this issue is another matter of course.

1 – Error Log Test

So if you clear out the SP error log (toolbox) then run one of these disappeared topics and then go back to the error log – is there an entry of any sort?

2 – Data Test

Go to the toolbox > Data Inspector and turn on the option to inspect the ‘Topic View Data’ – ‘spTopicView’ and then again run of the disappeared topics. Do you see a dump of the data displayed anywhere?

Was busy all day at work. So didn’t get a chance to look at it until now. I cleared the SP error log. Then tried one of the broken threads and it works now. I haven’t changed anything either. Hopefully it doesn’t happen again, lol. If it does I’ll see what I can find using the data test and sp error log.

sounds promising…  if not mysterious…