In file : vendor/ezsystems/ezpublish-kernel/eZ/Bundle/EzPublishDebugBundle/Collector/PersistenceCacheCollector.php

There is a typo on line 108 :

foreach ($traces as $traceHash => $traceData)

{ $traceCount[$traceHash] = $traceData['count']; }

The variables $traces doesn't exist.

I fix it with :

foreach ($call['traces'] as $traceHash => $traceData) { $traceCount[$traceHash] = $traceData['count']; }