Hi John,
The WW2.13_Ubuntu16.04_Vanilla.ova gives a very generic setup. You should "tune" your VM giving it a reasonable amount of cpu's, memory, and disk space depending on your load. Also look at the apache configuration, e.g. see http://webwork.maa.org/wiki/Installation_Manual_for_2.13_on_Ubuntu_18.04#Configuring_Apache,
especially
# For WeBWorK a rough rule of thumb is 5 MaxRequestWorkers per 1 GB of memory MaxRequestWorkers 5 MaxConnectionsPerChild 50