Save21 is the scene when he stays over, before the choice of bed/couch,
Save29 is the last save I had before that next update,
Save40 is just before he opens the diary.
I also seem to have an image file for a Save49, but no actual save file to go with it ... I just noticed that while getting these out, and I have no idea how that happened...
I don't think I was using any walkthrough, and like I said it's been a while, so I can't say for sure which path I SHOULD be on, but it definitely seems like there's an inconsistency.
Thanks. You were right. There is a problem with the conditions in the diary scene.
You are actually on the non-Nika-path and when you choose to sleep with her in the bed you didn't get to see the Milfy Nika sex scene. The condition/flag in the diary scene however, checks against the sex scene and not against the non-sex scene. Means, due to the wrong condition the game thinks you had sex with Nika which isn't true.
Here are your options:
1. You start a new game in Chapter 2 which automatically puts you on the Nika path.
2. You continue with your current save without seeing the Milfy Nika scene.
3. You modify your Milfy Nika dialogue file by removing the condition and choose to sleep with her in her bed.
Modification for Option 3:
Modify file
177_Day12NikaHome2_Bed.txt (dialogue folder) by removing the first two lines and save the file:
Relation |Nika.Path.True.1
Jump |177_Day12NikaHome2_Bed_NoNi.txt
Note: You don't need to extract your (Unrated_)/English.zip for doing this. You can simple navigate and edit the file from inside the archive file. After you saved your modification reload the language pack from the main menu and load your save.