If mongo is just a document database, there's really no reason to use it over elastic. The query story is slightly nicer with mongo, but we're not doing relational algebra here, right? Elastic crushes mongo at literally everything else.
I reported the issue, and thankfully I changed job and never had to deal with ES again. After a few years they contacted me to ask if the issue was still there, I said I had no idea.
I have no idea if the issue is still there.