I could not find a Govee incubator so I'm pretty sure the Govee is the instrument(s) to measure temperature and humidity. What incubator are you using? How do you control humidity with that incubator? Inquiring minds want to know. I control humidity with mine by filling different reservoirs in the base with water. Not all incubators work that way.
If I spill water when I refill those reservoirs the humidity can spike until all the surfaces that got wet dry out. Then the humidity stabilizes. What your graph looks like is when one of my reservoirs runs dry and needs to be refilled. That doesn't sound like a problem with the instrument at all, but like a problem with your actual humidity.
The wet surface area is what controls humidity, depth of the water doesn't matter except when it will all have evaporated. If you want to raise humidity with my type of incubator you need to add wet surface area. That could be putting water in a different reservoir, adding a sponge or paper towel in a way that it wicks water out of a reservoir and stays wet until that water evaporates, or add another water reservoir. Since you mentioned a sponge I'm guessing you have this type of incubator.
If I spill water when I refill those reservoirs the humidity can spike until all the surfaces that got wet dry out. Then the humidity stabilizes. What your graph looks like is when one of my reservoirs runs dry and needs to be refilled. That doesn't sound like a problem with the instrument at all, but like a problem with your actual humidity.
The wet surface area is what controls humidity, depth of the water doesn't matter except when it will all have evaporated. If you want to raise humidity with my type of incubator you need to add wet surface area. That could be putting water in a different reservoir, adding a sponge or paper towel in a way that it wicks water out of a reservoir and stays wet until that water evaporates, or add another water reservoir. Since you mentioned a sponge I'm guessing you have this type of incubator.