@GudNuf-Harley,
Not sure what exactly is causing the issue you’re having, but @Aaron (from RealMac) confirmed on this post that RapidWeaver supports TLS 1.2.
I know there’s a number of people that aren’t having issues with using FTPS. I don’t use FTPS myself, I always prefer SFTP, it uses SSH(Secure Shell), the same process used to administer the server.
I looked at Machighway’s support area to try and find any help on their knowledge base and they don’t even list FTPS or SFTP as being supported? The KB article for RapidWeaver publishing looks to be very old (pre RW6?), so not much help there.
Part of the error message that you posted (Problem with the SSL CA cert (path? access rights?), looks to be something being returned by the server. But since Machighway “backed out” the changes it’s going to be difficult to tell for sure what happened.
Their changes obviously “broke” more than just you so my guess is that there was something not quite right with their implementation. Hopefully they’ll do a better job testing (and update the KB area) before they attempt to go forward.