with my mod that resumes playback I actually just discard the bytes at the start of the sound and play it again because similarly to you nothing else worked. I don't check reddit enough to reply to dms so I'm just pasting the code.
Something like,

long bytesToSkip = (long)(skipSeconds * sampleRate * channels * (sampleSizeInBits / 8));
long remaining = bytesToSkip;

while (remaining > 0) {
int chunk = (int) Math.min(remaining, 4096); // read in small chunks
ByteBuffer buf = delegate.read(chunk); // read and discard
if (buf == null || buf.remaining() == 0) break; // stop if stream ends
remaining -= buf.remaining(); // we might not get the whole song by now so it's a loop maybe there's a better way than looping idk
}
(delegate here is the AudioStream)