So I've been working on this list of required actions on day 4. 14 at each location - it's no wonder that people seem to get stuck often. The numbers are the flags that the game requires to be set in order to progress.
Neuschwanstein (14 flags)
L = look (cursor), T = tour tape
579 Entry hall T
628 Small door T
580 Entry Hall Paintings left T
581 Entry Hall Paintings right T
582 Bedroom, either screen T
589 Bed closeup, first time T
590 Bed closeup, second time T
592 Bedroom painting (right) T
583 Study T
584 Chapel T
585 St Louis & Seraphim T
586 Living room T
587 Grotto T
588 Singer's Hall T
1031 Wolf Painting L
Herrenchiemsee (12 flags)
The game is very fussy here. For the entries marked Video, you must
see a video of Grace reflecting on what she sees.
For the others, it is enough that the player has seen the text.
995 "The people need to see you at the throne"
996 "You spoke so movingly of your torment"
997 Video "What were his last wishes?"
999 "If any more correspondneces come from Louis, they are to
be burnt immediately"
1000 "Remember that when the Great Friend arrives at
Neuschwanstein and we retreat to the hall"
624 Video "Grace sees, recognizes sleigh painting"
1002 "A group of men demand to take the king in custody"
1003 "Ludwig knows the conspirators will return"
1004 "At Berg, Ludwig seems more cooperative and coherent."
1005 "Ludwig's funeral procession marches through the streets of
Munich."
278 Asked clerk to see diary
279 Asked clerk about new Wagner opera
278 and 279 above in turn require
622 Video "I've got to see that diary!"
623 "Even after Wagner's death, Ludwig still showed signs of obsession with the composer"