iPod speaker hissing at volume above 30%

Alright so this is my dead dads old iPod touch 4, I always have it on a stand playing music through my AirPods when I sleep. Stupidly, I have a cup of water next to it and I must have knocked the water on it when I was sleeping.

I woke up and it was soaked and shut off. I immediately opened it and desoldered the battery and power flex. I soaked the thing in isopropyl alcohol and scrubbed with a tooth bruh. The iPod booted up but the speaker was only producing a hissing/static sound. This only happen when the iPod was up past 30%. So I changed the speaker about 5 times, same thing. This doesn’t happen with headphones or my AirPods.

I really wanna fix this as it was my dads, please help! :)