Polycom 650 soft buttons slow sticking and often non responsive

I have an issue with a client who has Polycom 650 phones, they are running 4.0.7 and they have two sidecar for speed dials with BLF enabled on all these speed dials.

The issue I am having is that the reception who operates these phones are complaining that they are often having to press the transfer button multiple times till it becomes responsive, the one press isnt enough, sometimes it takes 6 presses until it goes through.

I am wondering if anyone has experienced something similar to sticking buttons. Note that we have ruled out hardware due to spillage or broken button as the same thing is happening on another reception phone as well.

Any ideas or suggestions would be great.