Intermittent 500 errors

[instance1]

I have a strange problem and I have no idea if CL is involved or not. I have a customer site that serves up a relatively simple page, a visitor response form in Wordpress. Works fine about 87% of the time. It takes about 2.5 seconds to deliver the page. The remaining 13% of he time, the server sends a 500 error, but there is no information as to whats going on. Nothing in the error logs, either OS or Apache. No faults in CL.

Two questions:
1. Anyone have a clue as to whats going on?
2. Is there someplace else I can look for a hint as to whats going on.

[bogdan.sh]

Definitely there should be some errors in logs, in some cases error_log could be stored in same directory where wordpress is installed (or directory where PHP script is located). Check them please.

Also, check if customer is not hitting any lve limits, for example with:

 lveinfo --period=1h --id=UID

[instance1]

Thanks for the suggestion, Bogdan.

The root error_log had nothing, so I did a find on error_log, just in case the application was calling itself somewhere. Found a few errors, all of them months old.

lveinfo is clean:

lveinfo --period=1h --id=685
+----+--+----+----+----+---+---+---+---+
|From|To|aCPU|mCPU|lCPU|aEP|mEP|lEP|EPf|
+----+--+----+----+----+---+---+---+---+
+----+--+----+----+----+---+---+---+---+

I suspect its an application error, will look at scanning the code for calls to header() and see if I can find anything. I also tried looking at memory but when the page serves correctly peak use is only 32M.

[instance1]

Ive set his site up on a box without CL installed, and its exhibiting the same behaviour, although less frequently. Either way CL has been eliminated as a source of the issue. On to eliminating the next variable...

Thanks again for the help.