Symfony version(s) affected: 3.4.30

Description
When I run the cache:clear (cache:warmup) command the ReflectionClassResource::generateSignature method allocates a huge amount of memory and runs out at 64G (my max. setting). I attached the blackfire profiles. Everything else of the project runs fine.

How to reproduce
Sorry so far I couldn't figure out exactly what's causing this. Any suggestions what I can provide to solve this are appreciated. Unfortunately I can't share the source of the project.