As per this CUBA support forum post - Odd new error on deployed startup: "Exception loading sessions from persistent storage" - CUBA.Platform - I’m getting this in Jmix as well - but Jmix doesn’t use context.xml. How can this be switched off in Jmix?
Ideas here? 
If you are using JAR deployment, the following app property should help:
server.servlet.session.persistent = false
If you are deploying a WAR to Tomcat, create tomcat/conf/Catalina/localhost/<your-war-name>.xml file and add to it:
<Context>
<Manager pathname=""/>
</Context>