Build lighting stuck at 99% for High and Production Quality…i can build from Preview up to Medium in a few minutes but High and Production just don’t seem to finish…the SWARMS blue bar goes all the way to the end it doesn’t seem frozen and non of my Light map Res’s go above 512 only light in the scene is the directional light…any idea’s???
Hey man, have you ever tried to wait maybe a night your build finished?
I think it’s normal you see UE freezed. Many times, when i build, my pc die untill every build process is finished.
The last process (Encoding lightmass and invalidate previosly build) is very heavy for example. All of this depends by your system perfomances.
if you do not have enough ram UE & swarm crash before processing maps but if they are feezed i think you must only wait 
I’m facing the same issue right now actually and my high build speeds are usually 4-10 minutes. It built rather quickly before it started sitting at 99%. I had just begun a session so I haven’t used that much memory already. This issue didn’t arise until 4.9, so I’m gonna assume that that’s the issue.
Hello Mshep3D,
If you would please link me your DxDiag and what version of the engine you are using. I will then try and investigate this issue further.
Hello Mshep3D,
I haven’t heard from you yet. I was wondering if you had a chance to look into this further or if this issue has been resolved? Right now there have been a number of lighting build issues reported in the latest engine release. Please let me know if this is still an issue for you.
Sorry to hijack. This is definitely still an issue for us here at THREEONEZERO after the 4.9 update. I’ve been debugging lightmass a bit and have found that the mapping process threads never finish when you get to the 99% stuck situation. In LightingSystem.cpp in FStaticLightingSystem::ThreadLoop…the thread down counter is never incremented because of this condition:
Could it be some kind of race condition? I’ve found this affects maps that already existed in 4.8 before the update. Even if I delete all the actors and just leave one the same thing still happens. If I take an offending map and make it a sub-level of a new map I can build lighting on it but its not a viable workaround because once I bring in the other maps necessary I get the stuck issue again.
Hello guys,
Thank you all for your research and the reporting of this issue. This is a known issue and has been one of the larger issues with 4.9.
We are currently investigating this bug and it will be addressed as soon as possible.
This bug has been reported. The ticket number is UE-20782.
I will keep you all posted as this issue is handled.
Thank you,
Hello, I am having this issues, so unfortunately, I am reverting back to older version. Let us know when this is resolved. Thanks.