I have one customer who is getting a 503 error from the Backpack API when they sync. A lot of people should be running into this issue but I have not heard from anybody else. If you are having this problem, please let me know. I believe it is caused by a new behavior of the API that puts on limit on the number of requests you can make to it in 5 seconds. Syncing can potentially make many requests in 5 seconds and I think that’s what the problem is.