strange behaviour with org-indent-mode

[Eric S Fraga <e.fraga@ucl.ac.uk>]

Hello all,

for a very long time now, my default org setting has been to use
org-indent-mode with visual-line-mode activated.  This has been working
very well until sometime since the start of the new year.  I have two
symptoms now:

1. org files, especially large ones (250kB+), do not actually indent
   automatically.

2. my org capture templates are introducing spaces at the start of lines
   in the capture buffer to line up the start of every line.  Very strange.

I have org-startup-indented set to t.

I am having difficulties tracking this down because a) the lack of
indenting doesn't happen all the time, just most of the time and b) I
don't think it happens with emacs -Q.  I'm looking for suggestions on
how to track down the root problem or if this rings anybody's bells.

Before anybody suggests bisecting, yes, bisecting my configuration would
probably help but it is such a convoluted configuration due to my using
emacs for 30+ years...  I guess I really should bit the bullet and clean
up my initialisation files soon!

-- 
: Eric S Fraga (0xFFFCF67D), Emacs 25.0.90.1, Org release_8.3.3-535-g7213aa