They are likely reaching some limit set by your host on ‘long running’ processes. Are you using both pngout and optipng? If so, disable pngout, and see if that helps. Then, what levels are set for each of those tools? If you are not using the defaults (2 and 2), change them back to the defaults and see if that helps as well. The PNG optimizers are very CPU intensive, and a 352kb image could be complex enough to make them take quite a while, plus add in all the resizes that wordpress generates (default is 3, but themes and plugins can push that up to 20 or more), and it is very easy to exceed the limits set by your webhost.
Hello and thanks for your immediate response.
I have a vps server (3gb ram, 2 cpu etc)
I user both pngout and optipng
with the defaults (2 and 2).
jpegtran: Installed version: Independent JPEG Group’s JPEGTRAN, version 9a 19-Jan-2014
optipng: Installed version: OptiPNG version 0.7.5
gifsicle: Installed version: LCDF Gifsicle 1.84
safe mode: Off exec(): Enabled
Graphics libraries – only need one, used for conversion, not optimization
GD: Installed Imagemagick ‘convert’: Missing
Only need one of these:
finfo: Missing getimagesize(): Installed mime_content_type(): Missing
I deactivated the pngout and I put level 1 on optipng and it worked.
If you’re on a VPS, you should be able to increase the max_execution_time for php, and then you could bump up optipng a bit, and potentially even re-enable pngout.
