Random freezes on some CentOS 7 installations on HP Elitedesk 800 G4

I have been running CentOS 7 minimal on around 10 i7-8700 PCs in my organization. These machines are HP Elitedesk 800 G4 workstations (Hardware Ref. Guide ) (Maintenance and Service Guide ) (datasheet ). All work fine, except a couple which freeze randomly, requiring a hard reboot. I have looked at the var/logs/messages and dmsg but there are no errors which could potentially explain why the machine got hung. I am happy to provide more information if you need me to. PCs which freeze, and which do not freeze, are using exactly same apps for the same purpose, for local proxy use. I have checked swap usage by running vmstat with its delay and count but swap usage seems to be not exceeding the limit. # vmstat -a procs -----------memory---------- ---swap-- -----io---- -system-- ------cpu----- r b swpd free inact active si so bi bo in cs us sy id wa st 2 0 0 14922052 142620 734392 0 0 1 1 107 97 5 3 92 0 0