So, I went to Lower Guk 1 on Nightmare on my Bard, and I noticed my auto attack kept turning off. Then I noticed enemies weren't attacking me, then I noticed my damage songs would screw up as well.
--This is really hard to explain, so I recorded a video of it:
https://www.youtube.com/watch?v=GQJtTEU_hz0
I start with the graphics on High in the video, so everything is fine until I change it to Medium at the 0:50~ mark, when it breaks. I eventually turn the graphics back to High at ~1:50, kill off the enemies and the new enemies I pull are fine, but it breaks again when lower the settings back to Medium at ~2:30.
As for my troubleshooting:
I tried switching areas, it still happened.
I tried switching difficulties, it still happened.
I tried not having a charmed enemy, it stopped happening.
I have a feeling that it's an issue with my browser because Firefox updated for me to 30.0 RC1, as this has never happened before with the older version. I would move my save to another browser to test it, but I cannot for the life of me figure out how to move it. I got into the localstorage and saw my saves, but I just couldn't figure it out from there.
(Also, I still hope everything is going well with your new born!)
--Edit: I noticed a few other things, I don't know if any of these are related.
Sometimes bosses, such as Nagafen, will just not attack me. They just sit there and wait to die. I don't have a charmed enemy with me because I don't even know how to bring them into the fight. (on high graphics)
Sometimes the charmed enemy I have will break and just stand there, even when the charm breaks/gets canceled/times out they will still just sit there. (on high graphics)
I'm sure this is unrelated, but I also noticed that Largo's Euphonic Hymn (talented, but not 20) and Selo's Consonant Chain (untalented) overwrite each other.