Probably not the best place to post this, but I’m getting hundreds of “This map is using externally referenced packages which won’t be found when in a game and all references will be broken” map errors on every 4.7-4.9 project opened in 4.10. I never had this problem after updating to 4.8 or 4.9, so it may be relevant to this release. I’ll try to detail the issue on AnswerHub after I figure out what exact conditions trigger it, but right now I’m still trying to get rid of the errors, since the trick with renaming the project folder doesn’t seem to help.
EDIT: It seems that the errors may have been caused by changed DerivedDataCache entries in updated BaseEngine.ini, so my apologies for this premature bug report. I’m not usually the one to panic, but the sheer number of seemingly uncorrectable map errors overwhelmed me. :o