That's Onderon for you. Not much we can do there. Lowering graphics for the loading screens may work too.
That's if you break the rules in the Handmaiden Sister battle before they went hostile, then do the fight once more.
Don't!
Can't really fix this either I think seeing how the script for the battle can't be de-compiled .
No, sometimes some older saves seem to have trouble accepting new globals. Like here. Were you using an older savegame from before TSLRCM when starting it?
Usually that works fine but sometimes it doesn't.
Using the WARP cheat fixes this instance but don't be surprised if more glitches appear due to this. Make sure next time you start a full new game, that always initiliases the new globals correctly.
Holding off leveling them when leveling yourself usually gives you quite an edge. If you never leveled up Visas at all she's a pushover.
In other words; the difficulty of these 2 fights is entirely into the players hands...