Late Hatch Questions

I have a Farm Innovators Pro series (forced-air) incubator.
I have had a successful hatch before, but this batch seems to be sketchy.
Last batch of eggs didn't work out because my cat chewed the temp knob and cooked my eggs.
Sometimes he thinks he is a dog.

Anyway, this batch now was setup just like the first one. Temp has been good at 99.5 (used 2 meters), and knob has been shielded so no interference can happen again...and humidity standards are the same per instructions.
Candling seemed good like before. I have brown eggs so I really can't see anything, but I am able to tell the difference between clear and dark mass which usually increases over time. When I candle the eggs before lockdown, they usually have mass over 50% and you can see where the air space is. This time they were at 50% or less dark.

Day 21 would have been Dec 5th.
Nothing has happened. I checked the forum posts here to find out how to do the water test, and did that on the 10th. Out of the 40 eggs, only 1 was a sinker (which I had kind of suspected to be a quitter), but the others were low floaters (viable, developed eggs).
I swear 2 of the eggs shook in the bator (without my disturbance).
I patted all other eggs dry and returned them to bator asap, with some distilled water to bump up the humidity to 75.
I read one post from awhile back where someone had a few hatches at about 30 days. I will be approaching that time frame soon.
Any comments or suggestions?

The only thing different I can think about this time is that I added like 4 or 5 small black rocks (cleaned and sanitized) into the bator because I read someone using that technique to warm the cool spots.