The problem is, as I understand it, audio gets left in the delay or verb memory when you bypass the block, and maybe when you even change channels (not sure). Then, when you enable that block or channel later, the block outputs that audio like it would have had it been left active. Changing presets “zeros out” the memory, but changing scenes or disabling the block does not. This has been discussed in another thread previously, with really no good work-around.Parallel should be mute in. Series should be mute fx in. Does changing that help?
The pitch block actually does the same thing. I have one scene that uses it for a crystals sound. Sometimes when I switch scenes the leftover crystals come spilling out. Awkward.