Just saw this posted on Twitter:
I was told by Arq support that the issue of backward compatibility between Arq 6 and Arq 5, discussed on Arq’s blog on April 13, will not be fixed in Arq 6 at all. They “decided to make the compatibility mode a part of Arq 7”, according to the email I received.
So, they sold Arq 6 to customers, then found that it was not backward compatible and advised us not to use Arq 6. And not they are apparently abandoning Arq 6 and moving on to a new version.
Arq 6 definitely was a problem for some users. On top of that I understand it caught a lot of flak about the electron interface too, so I can understand opting for a clean start with the new UI, and a new version number.
As I stated earlier I really didn’t have any major problems and have continued to use v6. When v7 is released I plan to create a new bucket on B2, run a couple of moderate size backups, and use it for testing.