www.makemkv.com

So, I know the answer you're thinking, but it's not what you think. So, I have 2 SSDs in my PC. I have MakeMKV installed on the main hard drive & I have it rip discs to the other. Every so often, I check the drives & the main SSD gets slightly smaller when it comes to the free space left on it. Is MakeMKV responsible for this & if so, why & how do I get rid of whatever's being stored on my SSD?

MakeMKV maintains a log. It is (by default) overwritten each time you start the program. But it will continue to grow while the program is ripping disks.

You can tell it to not maintain a log, but that will be an issue if you have something you need to ask about. As I said, it's overwritten each time you start the program.