That may be one of the reasons why the Forum is experiencing instability.
The increase in visits makes the server load heavier.
Especially when Bitcoin will soon be halving, making many people start opening this forum, reading some threads, and commenting and there are more new accounts created.
If it was so then why each forum unavailability happens in the same time? About 6 am UTC? Hardly each time crowds of visitors come just at that time. It looks more like theymos said: some program starts working on the server in that time and overloads it. Main problem is to understand which program and why.