Actually we found this error in very fresh intatallation of Ubuntu 16.04 and postgres 10.5
After that we checked every configuration we have.
And only postgres 9.4 works as expected.
This issue is related to libxml2 limits - and it cannot to work with modern libxml2 libraries.
Yes, root cause is inside libxml2 code.
Can we protect postmaster from crashing from libxml2 error? There is a bunch of PG_TRY there, but it does not help.
Best regards, Andrey Borodin.