Opening and closing Xinha's HTML mode in IE corrupts all internal links in a document

After opening and closing HTML mode all the internal links are corrupted, something (either '/' or '/cms/') is prepended to the URL.

Create link in xinha field, open HTML view
<a href="testartikel_1">this is an internal link</a>
close HTML view, open HTML view
<a href="/cms/testartikel_1">this is an internal link</a>

Site now gives a pagenotfound

Reproduced on 2.16.06, 2.16.10, 2.16.05 instances