Bleeding Free Space

For at least the past two days, the My Cloud Home device I use has been losing free space even though I’m not actively transferring files to it. First sign of trouble was an email warning two days ago that it only had 600 GB left, which I didn’t think much of, now it’s down to 294 GB and dropping. I attempted to download the log files and the zip got up to and exceeded 1 GB before I cancelled it, making me suspect the logs themselves are filling up recursively for some reason.

I took the device off the internet, and the drain continued, so it’s not being hacked from the outside. I rebooted it and it continued immediately, suggesting that it isn’t grabbing data from another internal computer. I suspect the log is just endlessly bloating itself, but I can’t find where the log file is stored in order to attempt a mass deletion.

Please advise.