These are both about bodies… The headers causing that lock problem are not part of the body.
There is probably another configuration knob for them.
From: Yves Martin [mailto:email@example.com]
Sent: dinsdag 8 december 2015 12:10
To: Subversion <firstname.lastname@example.org>
Subject: Re: Unexpected HTTP status 400 'Bad request'.
In my Apache2 configuration, I have added "LimitRequestBody 0" and "LimitXMLRequestBody 0" to avoid such troubles with a 12-year-old-really-large repository...