Many times I have tracked an entire project and have used the audio mix down function to find that not only the mix down stereo file but also the original tracked project have either slowed down to half speed or increased to double time. I always record at 94/24, and so am compressing bit rates to either 44/16 (which slows down) or 48/24 ( which renders to double time). This has happened on multiple computers with multiple versions of Cubase, (now using 8 on a totally dedicated windows 10 system). I don’t use any 3rd party plugins, I use a 16 channel Mackie board to fire wire to computer. This has happened on and off for a decade and I am just about done with Cubase because of it. Thank you for any help or advice you can provide, I can’t be the only one who has this problem although I could find no reference to this issue anywhere.
goodfever
what version of Cubase do you use.
hello mroekalea, now I use Cubase 8.0 with a PC running windows 10.
It has to be something I am doing as it has happened with several versions of Cubase on several different PCs.
Post your mixdown screen and maybe we can help 
This shoudn’t be! You have configured things very basic and that’s the way it should be, the more options you activate the more complex your situation becomes.
I would suggest that you investigate what clock source your sound device (mackie FW interface) has.
From what I read I think you have a mackie Onyx mixer, the clocking should be set to internal, so your sound device uses it’s own internal clock, from what I read makes me think that your have clocked your sound device external.
By the way (not my intent to open a discussion) I myself would not record at 96Khz and then downsample at the end, I think sonically if recording at 44.1 Khz 24 bit is more then enough, especially when the mixdown is 24 bit 44.1 (or 48Khz).
Working with high samplerates is asking a lot of your device, 2 times regarding CPU operations & 4 x the bandwidth.
Have you also tried to mixdown al 96Khz and doing the dithering in a second step?
This way you can see for yourself if the mixdown in 96Khz also slows down.
It all comes down to breaking your workflow into small steps and see when behaviour changes you have something to investigate further…
Do you also have a screenshot of your sound device config? Mackie driver & cubase setup.