I have the same issue. The tiles for the "Shortcuts" are continually being changed to your Avast advertising partners and customers. I keep Shortcuts set for business sites I use for work. Today on startup and opening the browser, my shortcuts have once again been changed to Kohls, Amazon, Ebay, ect.
I have my desktop and lap top set to sync. The problem occurs on both.
In addition, there is obviously a bug in the sync in the feature. My bookmarks keep doubling and tripling. The "sync" feature keep copying my bookmarks back and forth between my laptop and desktop over and over again.
Finally, the browser was freeze issues. Several time each day, the browser will freeze all tabs and just lock up with no ability to close, renew, or anything what so ever. This frozen moment will typically last about a minute. Chrome and Edge do not do this. It is NOT a memory or internet issue on my hardware.
I am an AVAST Premium customer with multiple Avast products.