There is a minium duration of sound effects that can be edited in a sound layer.
If your sound effect is less than 0.22 seconds you can’t move or delete it once added to a sound layer. Longer than 0.22 seconds can be edited as expected.
I found the problem when adding a single dog bark, which was initially 0.1 seconds long. By adding 0.12 seconds of silence to the sound effect the problem vanished.
I have made some changes which I might fix the issue you described. Can you give this test build a go and let us know whether it does indeed resolve the issue? Windows 64-bit / Windows 32-bit / macOS / Linux
The advice to other Pencil2D users is to make sure your sound clips are at least 0.22 seconds long. If required to increase time length of your files, simply add silence @ the end of the file.
This isn’t important for exported projects, but for playing with Pencil2D adding the silence at the beginning if the clip will add time delay when playing. Thus they may give you a false impression of timing.