Jenkins stuck on 'Please wait while Jenkins is getting ready to work' after pressing 'Reload Configuration from Disk'

[Peter Toennies]

I am using Jenkins 2.138.2 on a RHEL7 x86_64 machine. It seems like I got Jenkins up and running. However, when I go to 'Manage Jenkins' and click on 'Reload Configuration from Disk' and press 'OK', Jenkins shows this is the browser:

Please wait while Jenkins is getting ready to work ...

Your browser will reload automatically when Jenkins is ready.

The browser seems to show this indefinitely. However, after just a few seconds, if I press the refresh key in the browser, it shows the Jenkins dashboard.

On the prior Jenkins version (2.89.4) that I was using on a ppc64 Big Endian machine, this was not the behavior. Within about 30 seconds the screen refreshed and loaded up the dashboard without me having to do any browser refresh. I don't think the /var/log/jenkins/jenkins.log file shows anything to cause a concern. It shows this line after confirming the reload:

Oct 25, 2018 5:46:30 PM jenkins.model.Jenkins doReload
WARNING: Reloading Jenkins as requested by <username>

And later shows (within same second):

INFO: Loaded all jobs

and later:

Oct 25, 2018 5:46:30 PM jenkins.model.Jenkins$5 runTask
INFO: Took 156ms for Finalizing set up by pool-14-thread-15
Oct 25, 2018 5:46:30 PM jenkins.InitReactorRunner$1 onAttained
INFO: Completed initialization

Between these lines, the most unusual thing logged are lines like this:

WARNING: JENKINS-27530: improper nextBuildNumber 0 detected in hudson.matrix.MatrixConfiguration@...

WARNING: JENKINS-27530: improper nextBuildNumber 16 detected in hudson.matrix.MatrixConfiguration@...

Does anyone have any ideas to resolve this problem? Also, the same behavior occurs if I navigate to the jenkins/restart URL and agree that I want to restart Jenkins.