mod_layout appending HTTP headers?

We recently came across the mod_layout module, and we'd like to start 
using it to include a header on some of our pages.  However, I am 
experiencing a very odd behavior that I'm not sure how to fix.  Using 
mod_layout 4.0.1a with Apache 2.0.43, I can cause a header to be added 
with the following config snippet:

<Location "/development/jim">
         AddOutputFilter LAYOUT html
         LayoutHeader /siteheader/header3.html
</Location>

However, mod_layout appears to be appending some of the HTTP headers 
for this page to the end of the HTML output!  The headers appended are 
random, and not always complete -- it looks like a random number of 
bytes of header are appended (maybe dependent on which thread is 
servicing the request?)  This is a very vanilla compile of Apache, with 
mod_layout as the only 3rd-party module in use.  I am using the worker 
MPM, which may be the only non-standard option (and even that is 
probably the most popular choice in Apache 2).  Has anyone else had 
this problem?

Jim Kane
Information Network of Arkansas
http://www.accessarkansas.org/ -- Your Bridge to State Government