Hello Federico,
Thanks for the input. Current score is only ten pages of string quartet music. Complex yes, but not vast. It suddenly stated after a Debian 9 update.
I love Frescobaldi, but the very sluggish response now of the text editor is unusable, and I have had to abandon it for Emacs. Emacs is great, but the indentation is abysmal, and just messes up really quickly. Caught between two unsatisfactory worlds now. I think I am going to have to take on the monumental task or rewriting from scratch the lilypond mode indenting and formatting engine. If I can achieve anything in that area, it may be a good side effect of this Frescobaldi problem.
Andrew