From:

https://jira.mongodb.org/browse/HELP-18938?focusedCommentId=3418563&page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel#comment-3418563

cleaned up and attached as bt.txt .

The "somap" field is present but mapped to an empty array in the backtrace here.
I don't know much more than that at this point, but it doesn't look correct!

Does this happen with all 4.4.1 backtraces or just this one?

This one is a seemingly infinite recursion failure, which might affect backtrace gathering? The backtracer is configured to show the first 100 frames and stop. This shows a full array of 100 frames at the same address.

{"a":"55FF0C178B7C","b":"55FF0A49B000","o":"1CDDB7C","s":"_ZN5mongo42DocumentSourceSingleDocumentTransformation9doGetNextEv","s+":"4C"},
... about 100 times.

...