DOCBOOK-APPS: toc missing cross references (fo)

Using fop17, with dbx1.29 and saxon 6.22

The cross references from a toc inclusion are missing.
The toc is being generated. 

I tried adding id values to the <chapter> elements
without any success. 

Error reported is:
WARNING: The following id's were referenced but not found:
"d36e94"
"d36e176"
"d36e91"
"d36e170"
"d36e164"
"d36e191"
"d36e159"
"d36e185"
"d36e99"
"d36e182"

Any help appreciated.
Regards DaveP