First off. Welcome.
As for the issue you describe. It could just be a worn and ageing Membrane causing the issue. On the other hand it may also me a sign of the keyboard controller chip exhibiting a fault.
For me, I would attempt getting hold of a replacement membrane to try first. Plenty in EBay, but make sure it is for the Samsung keyboard. A lot of the keyboards were also made by Mitsumi.
Failing that, see if you can buy a replacement keyboard controller board. Plenty on EBay at around £6 second hand.
