project folder size

Hi , I was wondering if you can help, if I start a project and write a 2 minute track I notice the folder size is anywhere from 7gb -9gb in file size, once I finished the song I then backup the project folder size is down to about 400mb , I choose the option to delete used files. this is great for backing up.
however if I then start to mix the track the project suddenly starts to creep up in size to about 2gb.
I can’t understand why this would be? is there any way too keep the file size down I’m running out of backup space or do I have to keep backing up each time.
I have tried going to the audio pool and deleting used audio but there is nothing un-used to delete
I’m using cubase 10,osx


I’m confused a bit.

Are you talking about the project file (CPR) size, or the folder?

Do you use any Arturia plug-in, by any chance?

sorry yes I meant project folder size and yes Arturia synth collection 7?


OK, then Arturia is the issue. This is known Arturia bug. They write some data, which shouldn’t be written, therefore the project size is increasing. As far as I know, they are working on the fix.

Please, get in contact with Arturia.

thanks Martin really appreciate the advice