I checked this morning and found that the iMac, when running 2.81a reported the error, but was able to render the Grease Pencil Monkey Object.

Hi Hans!

Thanks for the reply!

Hi Sybren,

The behavior sounds like what you're describing. The webbrowser never opened the link. I went to "My Data" on my own afterwards and found it empty. Then went back and encountered the error trying to resubmit.

Thank you for this incredibly helpful response!

Good catch!
I broke the image apart into two simpler images and forgot about it.

Hi Koil,

Thanks!
Sublime looks handy.

Hi Aaron,

Hi Aaron,

Hi Aaron,

Thank you for taking a look at it!
I tried sorting the grease pencil keys in the dopesheet and that definitely stopped the crash, so thank you for the workaround.
I wish I could answer your bigger picture question of how it got into the problematic state, but I'm not sure.
And your last point about layering in the grease pencil tool helps explain the confusing drawing behavior. I see now that I was assuming that layering would work as it does in the 3d view, more as a visibility flag than as a mechanism for determining the drawing order.

Quick followup.

Quick followup.

Hi Greg,