After using the system menu in administrator section, with debug system on, any and all subsequent action causes an out of memory error. Requires logging out to fix it.

Steps to reproduce the issue

Switch on "Debug System" (Global configuration, system tab)
Save and select System from admin menu
Pick any option

Expected result

Selection works as normal

Actual result

Out of memory error (see attached screen shot)
Any selection after this causes this same error.

System information (as much as possible)

Locally served site. Fedora Linux,

Additional comments

Turning off debug system restores correct action.