doxygen 1.8.5 generates invalid index.hhc?

[Amos]

I'm moving our api documentation system from doxygen 1.6.1 which comes with CentOS 6 to Doxygen 1.8.5 which comes with CentOS 7 and am hitting a problem with the CHM generation.

We use doxygen on Linux to create input files which are then fed to hhc.exe on Windows. hhc.exe fails on the input with an error like:

HHC5013: Error: URL reference in the TOC cannot be resolved: "a00001.html#intro".

And indeed the file "a00001.html" does not exist. All other files like a0000[2-9].html do exist.
The index.hhc line which causes this seem to be:

<LI><OBJECT type="text/sitemap"><param name="Name" value="Introduction to CellAppMgr"><param name="Local" value="a00001.html#intro"><param name="ImageNumber" value="1"></OBJECT>

There IS an index.html file with that title ("Introduction to CellAppMgr") but it's not mentioned in index.hhc.
The output from Doxygen 1.6.1 creates a file called "a00001.html" but it's not "Introduction to CellAppMgr" but appears to be documentation of one of the classes. Doxygen 1.6.1 output works OK.
The problem is persistent after multiple runs and happens across all our doxygen projects.
What am I doing wrong which causes this problem?

Thanks.

[Dirk Hoffmann]

One year later, no improvement?
I just hit the same problem. a00001.html is referenced where index.html should be, in files navtree.js and navtreeindex0.js.
Any hint?