Generally speaking, if the database keeps crashing this is commonly caused by the OS running out of memory and deciding to kill a process to reclaim memory. When it chooses mysqld then this is going to leave the database in a crashed state.
Starting off, when you look at /var/log/mysqld.log you'll see that these errors start being reported at a specific time.
Can you correlate that time to any events in /var/log/messages ?
Also, seeing as this is a VM, using the Hypervisor can you look at the VM's memory and CPU usage performance graphs at the same time that these errors start occurring in mysqld.log. It might show you that the memory was completely used at this time perhaps.
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