We have recently upgraded our Jenkins from version 2.68 -> 3.375.2

and as part of upgrade, we have also upgraded the Matrix auth plugin to -> 3.1.6 which is latest

After we updated the Jenkins and Matrix auth plugin we are not able to create any local user 

This is the below screenshot that displays the error after creating the user.

After we save the config and hit the url from the browser seeing this below error

More details:

I am running Jenkins on Tomcat and more interestingly not seeing any error in the logs

We have the same version running on our multiple env's but we are not seeing this issue there.

Can you please help if any config is getting missed here.