Pages with to many images on a typo3 site need to much time for imageprocessing to scale the images with graphicsmagic. The user gets the error: 500 Internal Server error.
The error_log says this:
mod_fcgid: read data timeout in 45 seconds
If I reload the page multiple times after a while all images are generated and cahed an it works.
My questions are:
The error message already tells you the reason: TYPO3 needs more time, but your web server hits the timeout of 45 seconds and stops waiting for the PHP process.
Thus, it's not TYPO3 that creates the error page, but your web server software (Apache? nginx?)
Increase the timeout, it should be influenced by FcgidIOTimeout when using Apache.