I have been playing around with learning Coldbox and have a small skeleton app created. I initially started with Coldbox 5 and got the basic skeleton app up and running. I then started to install modules from Forgebox one at a time. When I got to cbdebugger it installed fine and I got it configured properly, but when I went to enable it via the ?debugmode=true on the URL, the home page displays fine but at the bottom where the debugging information should be was an error (shown below).
First I replaced the Coldbox 5 folder with a Coldbox 4.3 folder and the error went away. I then put the Coldbox 5 folder back and switched from Lucee to Adobe CF 2016 and the error also did not reappear (even after reinit’ing the framework). So, it appears this error only happens with Coldbox 5 on Lucee. I did not try an older version of Lucee as it worked fine on that version of Lucee with Coldbox 4.3.
You should be able to reproduce this with your standard skeleton app with the cbdebugger module installed running with ColdBox 5 on Lucee 5.2.4.