This problem reappeared, on the same machine. I'll go and re-open the support case.
As you recall, the last time we looked at this on this system of yours we could not reproduce this issue, it was completely transient, which means its not a problem with modsecurity or even apache, its something else with the system. I personally logged in, and nothing was wrong with the system at that time. So if this is happening again, with the same system, then its not modsecurity thats the cause, something else changed on your system or with the host node, etc. and thats the cause.
As I recall you were using Virtuozzo and Plesk in that case, which are *huge* variables, particularly the VPS which has enormous effects on the entire environment and absolutely can cause bizarre behavior like this. And in the previous case, the problem just went away on its own, we didnt and you didnt change anything. Which means its something else entirely that caused this for you, such as the OS, virtualization technology, control panel, host node, etc. So, have you also opened a case with your control panel, virtualization, host node and OS vendors?
In short, its highly likely the same thing is going to happen again: we wont be able to reproduce this on the same system because its the VPS, OS or control panel software itself thats causing this issue for you. So I highly recommend you open a case with your OS, control panel and virtualization vendors. In all likelihood, as with the previous case you opened, which was also not caused by either modsecurity, or apache, this is likely to the be the same thing here.
In that case it was some artifact of the OS or virtual environment, and its probably the same thing here, which is not something we can fix for you.