Why doesn't imagick open some pdf files?

Question

Yii

php 5.6
imagemagick (8:6.8.9.9-7ubuntu5.4).
php5.6-imagick (3.4.3~rc2-2+deb.sury.org~xenial+1).
In general, such a task is to split pdf documents into png pages. The script works, but there are some pdf files that are not loaded via readImage(); However, I do not glorify any exceptions. On startup I say set_time_limit(0). Normal files can be converted indefinitely.
php5,6-pfm does not output anything to the logs. Still working.
At first I thought that the files were too large, although this happens with pdf sizes of 100+Mb, as well as with small 200Kb, for example. I did not find anything in common between these strange PDFs.
So, how to control the work of the script, and make it so that if such a pdf file is found, then move on to another one?

Answer 1

1. Look at the types of files that this version can work with.
2. Write to TP imagemagick.