@Ahoeben is correct. The monoprice mini has some bizarre layer heights like .13125. Cura 4.0 and 3.0 were aware of that and had profiles to match those layer heights natively. Cura 3.0 cut everything off at 4 decimal places though, which wasn't particularly awful since that covered most layer heights for the mini anyway. But now that its down to 3 I'm really held back. It's especially frustrating because if I go to a default profile that goes to 4 decimal points it'll allow it, but the second I touch the layer heights myself I'm stuck back at 3.
Another issue I've noticed is that my models are getting these weird holes all over the place ever since I updated. It's not particularly bad if it's my students models, like the one shown, but I work with fluids and these holes make the models I use to make a living unusable. I've gone back to 3.6 atm and the holes are there too. I'll have to figure out what version I was on before I lost all my profiles. It'll put holes in perfect cubes too. Which makes me think maybe it's a visual thing that I'm just not understanding? I loaded a perfect cube onto the platform and one of the edges was just removed.
Here's an image of the holes