Hello,
I do not have a crash report or anything technical for this. However, I can provide video if needed. Currently if I run a forge server with with a server side only mod, vanilla clients will not hear the proper sound. For example mobs walking sound like buttons and pressure plates being pressed. My mod does not modify sounds in any way. As a test I decided to run a forge client without my mod installed. With the forge client the sounds are correct. I then repeated this process with a forge client with my mod installed. I continued to get the correct sound, so I narrowed it down to most probably being a mapping bug in forge itself as only vanilla clients have this problem.
I assume the client is just misinterpreting the sounds sent over by the server.