This is a known issue with ALOT + MEHEM. When ALOT modifies the 500Choice file, the file is reconstructed in a way that seems to bring the original error in the file into execution path, not sure how.
ME3Log - Logging started.
BioSeqAct_PMCheckConditional BioD_Nor.TheWorld:PersistentLevel.Main_Sequence.Personal_Terminal.Give_Email_Rewards.BioSeqAct_PMCheckConditional_31: Serial size mismatch: Got 830, Expected 828
BioSeqAct_PMCheckConditional BioD_Nor.TheWorld:PersistentLevel.Main_Sequence.Personal_Terminal.Give_Email_Rewards.BioSeqAct_PMCheckConditional_32: Serial size mismatch: Got 830, Expected 828
SFXSeqAct_SetMusicID end002_anderson_end_m_D.SFXSeqAct_SetMusicID: Serial size mismatch: Got 382, Expected 15016
ULinkerLoad::operator<<, Bad name index 252416/1785, Archive ..\..\BIOGame\DLC\DLC_CON_MEHEM\CookedPCConsole\BioD_End002_500Choice.pcc
This log however is useful, and may help us find a way to automatically repair this file before ALOT is installed. For now you can delete BIOGame\DLC\DLC_CON_MEHEM\CookedPCConsole\BioD_End002_500Choice.pcc and then run AutoTOC from Settings/Game Utilities/AutoTOC. Doing this will lock you out from installing more textures, but it will avoid this error as it is will revert to the extended cut version of the file.