i2s sginals and noise when connecting a 10cm cable
At 49MHz, a 10 cm cable becomes a long line and needs to be terminated to avoid signal reflections. The problem is that termination works well on point-to-point connections, and not so well on buses.

If your connection is unidirectional P2P, I would try to source-terminate all signals at the transmitter's side. Otherwise, you'll have to look at your signals with a scope to see what kind of noise you're getting exactly and what could be done to deal with it.