Greetings all, I searched and did not see this issue reported, though I did see one which may be related that has been closed. I wanted to share this in case others may be suffering from what I was and not even know it.
Normally I trust my slicers on the nit level details of the slicing, so I do not tend to walk through every layer before a print (maybe I should), but recently I noticed a strange/problematic behavior. I have always used the drop to bed feature after importing a model, in the past and typically it will drop the model onto the plate from above and let it settle as gravity would have it (if it's above the mat, or askew slightly it will fall flat). When working on my own design though, I noticed the slicer was making a strange out of place line on the exterior wall. A vertical path was there, and it did not need to be. Example 1 below shows a normal 90 degree line as expected. Example 2 highlights something new in this layer (the previous layer did not have it) which is a strange ~83 degree line appearing out of nowhere in a space that nothing in my model should be causing it.
Looking VERY closely at the build plate, zoomed way in I was able to see what's happening. In the last example you will see that the object is a microscopic amount off level, I couldn't even see it naked eye without zooming this far in and lining the horizon up exactly. This behavior causes the slicer to make a LOT of strange/poor decisions, and while the prints usually work and you are not aware of it, internally t hings are messed up, to the point that I have had structural problems etc. because some layers would be half baked spanning 2 layers when parts should be all on the same layer.
The workaround? If I use the place surface on bed option and pick any face on the bottom, it works as expected and the entire model lays flat. Looking at the same slice afterwards the stranger lines are gone, the surface is clean, and my print time has gone down. I am not sure how long this has been happening, but I now know why some of my previous print jobs went wonky on me. I hope this helps anyone else if they are pulling their hair out over inconsistent print results too!
To devs, I assume this is not the desired behavior of the drop to bed function? If not, would love to see a fix in the next version