Hello,
I've a plesk 17.5.3 on a centos 6.9, with apache/2.2.15
It basically runs a single domain, that use 15Gb and have a traffic of 150Gb/month.
It is 2 month from now that on sunday at 3:50 one apache process takes 99% of CPU.
The server runs almost two year with no problem.
No crontab runs...