Strange behaviour of Chord Staff

[Joe Wilkinson]

Hi Richard,
Using the same template as I have used many times to simplify the use of 
Eb and Bb instruments in our small church Band (attached), I have 
started getting this error (attached pdf).
The top stave should be a chord staff. It is currently blank and not a 
chord staff but has a mix of notes from Staffs 4 and 6.
It produces even more interesting results as a Chord staff.
But it is blank.
I have obviously done something recently, but have no idea what or how 
to correct it. I have done the obvious of deleting the top staff and 
creating it again.
No Joy. Help? I am using version 2.6.10
Best wishes
Joe

temp0812.denemo
Description: XML document

temp0812-Default Score Layout.pdf
Description: Adobe PDF document

EbBb44.denemo
Description: XML document