The disc doesn't have AACS, but it does have structural protection and possibly playlist obfuscation.
I've attached my log.
--- Errors emitted by job 'Multiplexing to file "bittertea.mkv" in directory "D:\"' started on 2017-09-13 11:14:29 ---
The track number 1 from the file 'D:\BITTER_TEA_OF_GENERAL_YEN\BDMV\PLAYLIST\..\STREAM\26507.m2ts' cannot be appended to the track number 1 from the file 'D:\BITTER_TEA_OF_GENERAL_YEN\BDMV\PLAYLIST\..\STREAM\24464.m2ts'. The number of channels of the two audio tracks is different: 0 and 2
I solved the problem with eac3to. Apparently the audio track has something called "dirty PES bytes". I don't know what that is, but eac3to does and fixed it.