I found some more bugs while playing through a route without Jill nor Isabella, but for the first two bugs, it might be due to the save files.
10. In the Candy Factory, and in the area where you would feed the dev girl the mega potatoes, if you jump or bounce you way to her, the dialog option for telling her it's her birthday is there. However, if you decide to move back around the area you entered, but not leaving while also not jumping or bouncing, then move normally back to the dev girl and talk to her again, the dialog option for telling her it's her birthday will disappear.
11. If you feed the dev girl the mega potatoes again, and then you tell her it's her birthday, her VN art goes from immobile, back to the somewhat fatten stage for the dialog. And then after getting the shake, if you talk to her again, her VN art goes back to immobile.
12. In Heatton, if you enter in any of the residents houses or the armory, you can jump or bounce out of the area and even jump into the other buildings.
13.If you don't have Jill in the party when starting the slime layer, somehow a dialog for Jill suggesting to put her in the active team still pops up.
Also, playing through the slime lair feels quiet if you don't have Jill or Isabella, especially upon entering their house as there's no dialog, meaning some players won't even know it's their house.
14. When I got the spectacles from the dev girl fight, I first thought it was for equipping it on the head, then when I tried to equip it for one of the members, I couldn't find it and almost assumed it was bugged. However, when I was checking the inventory to be sure I have it, turns out it's an accessory and not for the head. I don't know if this is intended to be an accessory unless it was meant to be for the head.
15. When Nessie enters the second stage of either waterlogged or slime filled, her VN art shifts up a little bit, and then when going back to normal, her VN shifts back down.
That's all I've encounter so far, but I'm wondering something out of curiosity. Will we see more of At'lass in the future? Mainly because I've realized that we only see her at the beginning of the game and a little bit at Floater's Woods. Wishful thinking that she'll actually be the last recruitable party member...