Here is the offending loop:

while ( !endNode.isWrapped() ) {
	endNode = endNode.getParent();
}

This happens when a particular selection is copied (unclear what), but the worst that can happen is the copy doesn't work.

Reproduced with one of the cases from the log, but can also be reproduced in standalone.

1. Open aliens.html
2. Create a selection starting in text and ending in a block alien
3. Hit copy with the console open and observe the error

Bisect somewhat unhelpfully blames this on this commit from 2014 where I got rid of the shields code and replaced it with getClientRects: https://gerrit.wikimedia.org/r/c/VisualEditor/VisualEditor/+/139805

Basically this bug has been present ever since we moved to the current way of dealing with block nodes in the surface.

Change 623025 had a related patch set uploaded (by Esanders; owner: Esanders):
[VisualEditor/VisualEditor@master] ve.dm.Document: Fix shallowCloneFromRange when range is inside alien

https://gerrit.wikimedia.org/r/623025

Change 623025 merged by jenkins-bot:
[VisualEditor/VisualEditor@master] ve.dm.Document: Fix shallowCloneFromRange when range is inside alien

https://gerrit.wikimedia.org/r/623025

Change 623655 had a related patch set uploaded (by Bartosz Dziewoński; owner: Bartosz Dziewoński):
[mediawiki/extensions/VisualEditor@master] Update VE core submodule to master (15186ed26)

https://gerrit.wikimedia.org/r/623655

Change 623655 merged by jenkins-bot:
[mediawiki/extensions/VisualEditor@master] Update VE core submodule to master (15186ed26)

https://gerrit.wikimedia.org/r/623655