This was reported to mkdoc-dev on 23 Feb 2005 and the thread continued in March.
With MKDoc 1.4 you could havea directory like /bread-crumb-trail/ with a en.html and a tr.html file in it and on Turkish pages the tr.html template would be used and on English pages the en.html fragment would be used.
This is broken in MKDoc 1.6.
What happens is that the first language version to be accessed appears to be cached and then pages of either language just display the fragment in one language.
The only way to make things work for every request is to stop and start apache between requests…