LrC stalls during synch with LR cloud

I have been using Adobe LR with 1GB of cloud storage (which I use almost fully) - a total of ~ 50000 photos.

I recently also purchased LrC to be more flexible and have multiple catalogues.

All programs are updated to their respective latest versions.

Now, I want to have one Catalogue in LrC  which is fully synched with the photos in the LR cloud.

When I start the process on my Windows 10 notebook LrC crashes constantly and I don't know why because there is no error message.

When I start the process on my Mac, memory use by LrC does sometime blow up. While it generally uses ~ 1-2GB it then uses the maximum of around 60GB and stalls and I have to force quit it (I get a message by the OS telling me to do so).

Alternatively, I would be happy to export photos and import them with ALL changes that I applied in LR to LrC. However, that did not work either - it seems that exposure settings were not transferred.