Seems to be working in the latest version. Just had a moderator test it out.
What version are you using. That was an old issue, that was supposed to have been resolved.
Has this structure been saved first befor light mapping?
RIP
Intel(R) Core(TM)2 Quad CPU Q6600 @ 2.40GHz, 2400 Mhz, 4 Core(s), 4 Logical Processor(s), 8gb RAM, Nvidia gtx660, Windows 7 Pro 64bit, Screen resolution 1680 x 1050.
New:
Intel(R) Core(TM) i5-8400 CPU @ 2.81GHz, 12GB RAM, Nvidia gtx660, Windows 10 Home 64bit, Screen resolution 1920 x 1080. System Passmark 3774