rekordbox 6 - permanently upload data

I am using the free plan of rekordbox and I had problems with analysing.

Now I realized that rekordbox is permanently uploading data to the internet. In addition it uses nearly the full available bandwith of 10 Mbit/s in my case. This seem to be a ton of data which is being uploaded.

So what is the data which is uploaded if I don't use a cloud service?
Can this process been stopped if I don't want Pioneer DJ to get all this data?
Any impact on GDPR?

Btw. After I stopped the upload via my firewall, all pending analysis had been executed immediately.
Even if I would be ok with the upload, local analysis of tracks always must have a higher priority to be executed.

This is all from rekordbox:

As soon as rekordbox is closing the upstream stops.

When starting rekordbox 6 with a disabled internet connection, the start of the software is taking ages.... I thought even that the software will never start....