Here's a bug I noticed after using Serum and Serum 2 user presets:
If you have more than 68,416 presets in total (including factory, serum and serum 2 user presets), the presets won't load from Serum 2 user presets from the FRONT PAGE DROP DOWN MENU after the 68,416 th preset! It will display the last one loaded instead.
But they will still load from the other menu (the one when you click on the square just left of the "menu" icon).