Jenkins job will not accept git configuration. The scm settings rest when the job saves – CentOS

I have been beating my head on this for some time, and I am hoping that someone can point me in the right direction.

I have (what is currently) an up to date version of Jenkins 2.224 running on Centos 7. I have the git plugin installed and up to date at v4.2.1. All plugins are up to date.

I have created a freestyle job, and am attempting to have it poll git SCM. I put the URL and creds in, and Jenkins seems happy. I click ‘apply’ and then ‘save’. Now, if I open the job again, the SCM section is back to ‘none’. OK… What?

I have checked the Jenkins logs, but found only shutdown and start up messages.
I checked the tomcat logs, but found nothing that looks helpful… at least to me.
I checked for system messages, and found nothing.
I opened the job location files and poked around. I found the ‘scm-polling.log’ but nothing interesting in there. It worked once I guess… but the config.xml scm section is just:

  <scm class="hudson.scm.NullSCM"/>

I found an example of the config.xml with a git section, and I edited that, and paste it in my job’s config.xml. Now, the job definition in Jenkins shows the git config… cool… I guess… BUT, when I changed the number of builds to retain (I changed no part of the git config), the git section is removed again.

Anyone have any idea what is causing this?
Is there a log I failed to find that might hold the error?