Hi,
Missing informations:
* SCK frequency
* wiring, type, characteristic impedance
* if used: termination resistor value
* if used: series resistor value
* scope picture of the signal at the receiver side
Fail is quite expectable.
Single ended signals (combined with not impedance controlled wiring) are not useful for long distance. Buffered or not will not make much difference.
--> Use differental signaling and impedance controlled twisted pair lines.
RS422 or LVDS.
If you insist on single ended wiring, then you need some series resistors to reduce ringing (echo), maybe some kind of termination will help. Next step is to reduce SCK frequency.
Klaus