Expected array for frame error in zend2 framework

I'm having a problem which only occurs on my live system. The system works with zend2 and PHP7. The problem is that my warning.log is flodded with following message:

2017-07-10T08:43:50+02:00 ERR: Expected array for frame X {"Code":0,"File":"vendor/zendframework/zend-log/src/Formatter/Base.php","Line":105}

The X is a number between 0 and 25. At the end of these numerous errors I get another one:

2017-07-10T10:29:34+02:00 ERR: Unable to write {"Code":0,"File":"vendor/zendframework/zend-log/src/Formatter/Base.php","Line":111}

I don't see a proper stack trace to see where this is coming from and I can't reprocude the problem on my local dev machine.

Any help would be appreciated.

Edit: A collegue told me that this error message comes from the C-level of PHP7. Has anyone an idea how to get a proper stack trace? Or what the problem could be?

I tried to catch the error with

...try{
    return (string) $value;
} catch(\Throwable $e){
    file_put_contents('error.txt',var_export($e,true),FILE_APPEND);
    file_put_contents('value.txt',var_export($value,true),FILE_APPEND);
    return (string) $value;
}

but it seems like this error could not be caught. This suggests that the information of my collegue is correct.