uncontrolled and erratic preset preview
in the latest version of LR (V9.1, running on OS Mojave) I experience in erratic but recurring cases that the active image in Develop mode changes to display completly different style, what most probably must be one of the presets, but without hovering the mouse over the presets on the left hand side. The only way to get back to the actual view of the image is to select another one and then back to the one in work. The preset is also not actually applied to the image (not in the history). It's just a displaying issue.