Open provided BugDemo.uproject, Base.umap will load.
Try deleting or renaming any Actor from the World Outliner.
Some Actors are referenced externally and it may ask “Do you really want to delete it? This will break References.”
Yes or No, it does not matter. The Editor will now hang forever with “Updating Asset References”.
Some notes:
Loading both the provided Sequence files into memory brings back correct behavior.
Deleting either Sequence file also brings back correct behavior. Strangely, they are both needed to trigger the bug.
There are no circular dependencies in the files, but the buggy code exhibits a circular hang with low CPU and Disk usage. This is not related, but the Sequencer is storing garbage references to unused levels from previously possessed actors that are now deleted or replaced with actors from new levels. Reference Viewer is now showing these orphaned links to older levels at 4.18 while they are completely hidden and uncleanable from the UI. This bug also happens with Sequence files without the old orphaned level references. It is also triggered with references from other levels, and not just Sequences.
After looking through the project provided I found that the sequences have bad references in them. After removing these the error no longer occurred. Can you reproduce this issue in a clean project? If so,could you provide a detailed list of steps to reproduce this issue in a clean project?
Thank you for inspecting this issue. The problem is more insidious than it appears at first. As noted above, if you open and load the Sequence files into memory, it will mask the problem. Such is not an option in the main project with numerous files. Even if you delete and empty the entire contents of the Sequence files, save them, exit the the Editor and come back, the problem persists! As noted, the Reference Viewer is showing links at 4.18 that were garbage accumulated from previous deleted references. This is not a user error and is confirmed here in another bug report:
Even if the problem was simply missing links, can you imagine a web browser stuck, even after aborting the action?
Here I am providing even a simpler version of the BugReportV4.zip with just 2 Sequence files, and their contents are completely deleted and emptied. You will still get the hang, but Before you open and see the empty Sequence files. There seems to be no way for the user to fix these bug corrupted files as they are completely emptied from the UI.
This needs to be reported to the 4.18 people in charge of implementing the new Cross-level Actor References/Soft Object References. They need to catch the hang in their debugger with the source code.
I have reproduced the Bug in a clean project and steps as you have asked. It is now confirmed this bug is not caused by bad references or file serialization debris from older bugs. It is also present in simple Level references which renders 4.18 unready for prime time development. So I have created a newer, simpler bug report. If I was in charge of developing and fixing these referencing systems however, I would still want to see the reports and examples here.