See test file and its SVG export with missing line joint and line cap attributes.
Created attachment 88504 [details]
ODG test file (rectangle with miter line joint and line with rounded line cap)
Created attachment 88505 [details]
bad SVG export
Laszlo Nemeth committed a patch related to this issue.
It has been pushed to "master":
fdo#71137 fix linecap and linejoint in SVG export
The patch should be included in the daily builds available at
http://dev-builds.libreoffice.org/daily/ in the next 24-48 hours. More
information about daily builds can be found at:
Affected users are encouraged to test the fix and report feedback.