Logic Pro 8 Lost mix


I completed yesterday's mix, pleased with it.
I save after almost every action - it's a habit.
It included resetting a guitar EQ to minimise finger slide ( discussed elsewhere on the forum)

It also included lots of manual Volume edits of vocal and instrumental tracks.

Today the mix is completely different - although as a standard, the guitar EQ is as edited, so I did save as usual.

One thing I notice is that many (but not all) of the track automation lines begin after the beginning of the song - meaning that the first node starts on bar 5 or later of a song starting on bar 2, with no line at all from bar 1.

Something seems to have hit my song but I haven't a clue what it might be.

the song is quite large, by my standards. 50 tracks and lots of plugins.

I haven't moved most of the regions affected, not have I cut or inserted any time.

One thing which has plagued me for ages is that after 'deleting unused tracks' or deleting unused versions of a multiole 'cycle record', all the remaining regions will shift up the tracklist and I'll need to carefully move them all back down. I'd love a solution for this, although I doubt that it's the cause of my mix problem as I have set automation to move with regions.

Is there a known bug that might be at work here?