Take a look at this thread where @anon18523487 has identified a scenario for me where the new “Downloads” doesn’t gracefully deal with lingering SRT-related issues as well as “Sync” did.
Obviously there’s more work to be done on the Server end to get “Downloads” to work as smoothly as “Sync”, especially for us long-time Plex customers who have libraries that date back to the pre-“Plex Movie” (aka “legacy”) days, but I am finding that, one-by-one, doing a “Refresh Metadata” on my failing downloads has been making (most of?) them succeed.