I think this might be due to the RadioItems and Checklist components not being used as inputs for any callback in that example. This has come up before here. I think this will right itself once you wire them up as Inputs for callbacks, which I’m presuming you either meant to do or do soon.
Yeah, you can’t have multiple outputs for a callback, although this might change at some point. If the elements to be cleared are located contiguously within the layout you could just have that part of the layout, which includes all the things needing clearing, be (re)generated through a callback (both on initial page load and for when you press the clear button).
Otherwise you do need four different callbacks. Using the app.callback function as a function rather than a decorator can make this a bit more streamlined. See this post for inspiration.