So I have three issues that seem related to Addressables vs nested timelines. In troubleshooting, I found some old posts for similar issues with AssetBundles, but nothing regarding these issues and Addressables. For context, I am using Unity 2019.3.6f1 and Addressables 1.7.4. 1. The first issue happens sometimes when opening a scene using Addressables, but not always (maybe 1 in 10 or 1 in 20 times) and it only started when we introduced nested timelines. It gets to 90-ish% complete and then flashes this error: Code (CSharp): Assertion failed on expression: 'pred(*previous, *i)' I personally get the error 68 times before the game crashes with a null pointer exception on my main timeline. This is similar to this AssetBundle bug (link) that was fixed in 2019.1. 2. The second issue is in the timeline itself when the scene does load, the nested timelines are not found. I was able to duct-tape fix this by putting all of the nested timelines into the same Addressable as the main timeline, but ideally, I shouldn't have to do this. This is similar to this AssetBundles bug (link) which appears to be pending solution. 3. Regardless of how I handled the previous issue, the bindings are broken. The source object in this case is a GameObject in the scene hierarchy, but I've tried making it an addressable prefab and included it in the same bundle as the timelines, but it produces the same result. This is similar to this AssetBundles bug (link) that appears to have been fixed, though this particular thread doesn't specify when. If anyone has any advice, I'm happy to listen. Otherwise, I guess this is a heads up for the Addressables dev team.