Turns out my hosting company security rejected edit updates where the pages were of significant length with a number of external links - they considered it a security risk. This explains the inconsistency on when I saw the error. I am having the issue resolved server side.
I'm having similar problems to this issue:
https://forum.dokuwiki.org/thread/6492 but I think it is different because it is only on certain pages that I am experiencing the problem - particularly long pages. I've searched for a dokuwiki page edit limit (if there is such a thing) but can't find anything. I hit the save button after an edit. A trace on Firefox console shows that I get a regular 302 on POST but the return header returns the 'start page' = doku.php:
POST http://aker.deprofundis.co.uk/doku.php?id=aker:collected_works:cw5&do=edit&rev=1379030980 [HTTP/1.1 302 Moved Temporarily 1319ms]
GET http://aker.deprofundis.co.uk/doku.php [HTTP/1.1 200 OK 495ms]
It only happens on particularly long pages so I don't think it is to do with URL re-write problems (
https://www.dokuwiki.org/rewrite).
Any way to trace where the error might be?...I'm lost.
Thanks