[Solved] Project's overall level dropped by about 6dB

I've been tweaking a project for the last few days and exporting mixes, each with only minor difference from the last. But today after a few small amendments, I exported the latest mix and noticed that the Master bus meter level seemed low. Comparing the resulting waveform with yesterday's mix (using Audacity) confirmed that there was a significant difference in overall level.
 
So I opened an earlier version of the project and took a screenshot of console view to compare settings with the current version. The levels (volume and) of all the buses are pretty much identical. As a workaround I increased the levels by 6dB of the 3 buses that route directly to the Master bus and that has brought the overall level back to normal. But I would really prefer to know the cause of problem.
 
I know what some of you are thinking. Offset Mode! But no, I've checked and it's not that. Does anyone have any other suggestions about what else I could check?

Bristol_Jonesey
Have your main out faders been lowered? Master buss?
Check any Fx on your master buss.
How many pairs of outputs are enabled in your mains?
How are you exporting, using Entire Mix or Main Outs?

Mains out still set at zero, as always.
Only one effect on Master and it hasn't altered.
Only one pair of Mains.
Exporting entire mix.

Something happening to me which could be related, is that this project I've been working on for a week has tracks and buses not opening up at consistent levels.  I mean I'll open the project after working on it the previous day, and the relative levels are definitely, noticeably different than when I left off.  To compensate, I keep tweaking the gains to approximate the balance I had previously - and it's spooky, and a PITA.  X3 has only been used for a few weeks now, this is the first big project with it, and I can tell you, nothing like this ever happened with 8.5.
 
Randy

Anderton...Check your volume automation lanes, which may be "taking over" from your faders...

Ah ha!  That sounds like a promising explanation- When I open up Sonar a bit later this morning, I'll look into that Craig.  I haven't dealt with, or even looked at automation lanes yet - I've been doing lots of standard automation, recorded in real time - Maybe I somehow accidentally turned on an automation lane--?-- Not sure what I'm talking about, I need to take a look first.  Thanks, Mr. A!

Randy

Check your offset mode and check your entire signal chain before the master bus. Make sure your tracks are routed correctly and make sure you exported it correctly using the correct exporting source.
 
All tracks go to the Master
Sends go to buses
Busses go to the master
Master goes to main outs
*Export using the source Entire mix or Main outs


CJ
 
 

Sanderxpander
Any plugs active on the ProChannel on the master bus? Or some other important submix bus...

Only the ProChannel compressor on one of the submix buses.  Disabling it doesn't make a big difference. 

EUREKA!
It turned out that the ProChannel compressor was active on the Master bus. Turning it off brought the level back to normal. PHEW!
 
Use of this ProChannel module on this bus was not intentional and I don't know how it happened, as I didn't even have ProChannel visible on that bus in Console View. Nor did I intend to use any of the ProChannel modules on the Master bus, although I did use some of them elsewhere.
 
Anyway, thanks for all the suggestions (some of which were certainly on the right track).

Grem
Kev could you have possibly engaged the compressor *thinking* you were working on another strip?

That's probably what happened.
 
EDIT:
Or maybe not (see next post).

I posted about something similar just a week or so ago. QuadEQ became "active" on every single track, and the low frequency gain was turned all the way up on every track. Took me awhile to undo it.
 
I never use Quick Groups either, guess I need to read more about it.
 
Regards,
Dan