TypeError: Cannot set property [HTMLInputElement].src that has only a getter to value  #309

I am getting this error while running. It doesn't seem to stop things from executing, but I thought I should figure it out before it causes problems down the line (or maybe already is and I just don't know it yet).

Feb 08, 2021 5:06:05 PM com.gargoylesoftware.htmlunit.WebConsole error
SEVERE: ERROR TypeError: Cannot set property [HTMLInputElement].src that has only a getter to value 'images/dashboardList.png'.

When I turn on logging for WARNING and above I see these warnings:

Feb 08, 2021 5:12:52 PM com.gargoylesoftware.htmlunit.IncorrectnessListenerImpl notify
WARNING: Obsolete content type encountered: 'application/x-javascript'.
Feb 08, 2021 5:12:52 PM com.gargoylesoftware.htmlunit.IncorrectnessListenerImpl notify
WARNING: Obsolete content type encountered: 'application/x-javascript'.
Feb 08, 2021 5:12:52 PM com.gargoylesoftware.htmlunit.IncorrectnessListenerImpl notify
WARNING: Obsolete content type encountered: 'application/x-javascript'.
Feb 08, 2021 5:12:53 PM com.gargoylesoftware.htmlunit.IncorrectnessListenerImpl notify
WARNING: Obsolete content type encountered: 'application/x-javascript'.
Feb 08, 2021 5:12:54 PM com.gargoylesoftware.htmlunit.IncorrectnessListenerImpl notify
WARNING: Obsolete content type encountered: 'application/x-javascript'.
Feb 08, 2021 5:12:54 PM com.gargoylesoftware.htmlunit.IncorrectnessListenerImpl notify
WARNING: Obsolete content type encountered: 'application/x-javascript'.
Feb 08, 2021 5:12:54 PM com.gargoylesoftware.htmlunit.IncorrectnessListenerImpl notify
WARNING: Obsolete content type encountered: 'application/x-javascript'.
Feb 08, 2021 5:12:54 PM com.gargoylesoftware.htmlunit.IncorrectnessListenerImpl notify
WARNING: Obsolete content type encountered: 'application/x-javascript'.
Feb 08, 2021 5:12:55 PM com.gargoylesoftware.htmlunit.IncorrectnessListenerImpl notify
WARNING: Obsolete content type encountered: 'application/x-javascript'.
Feb 08, 2021 5:12:55 PM com.gargoylesoftware.htmlunit.IncorrectnessListenerImpl notify
WARNING: Obsolete content type encountered: 'application/x-javascript'.
Feb 08, 2021 5:12:55 PM com.gargoylesoftware.htmlunit.IncorrectnessListenerImpl notify
WARNING: Obsolete content type encountered: 'application/x-javascript'.

and additionally (doesn't occur every run):

2021-02-08 17:12:58.329:INFO::main: Logging initialized @8155ms to org.eclipse.jetty.util.log.StdErrLog
Feb 08, 2021 5:13:00 PM com.gargoylesoftware.htmlunit.WebConsole error
SEVERE: ERROR TypeError: Cannot set property [HTMLInputElement].src that has only a getter to value 'images/arrow-up.png'.