Southwest railway ticket machines

[puffing billy]

Have the ticket machines at SWR stations been reprogrammed to restrict the destinations that can be purchased as a Z6B extension? At Putney station (after 09:30) I used the "ticket from other starting station" option to select Z6B; and specified Oxted as my destination station only to get the message "no valid tickets for that destination" (or something similar). Although Oxted station is not served by SWR I'm 99% sure I've used the same type of machine at an SWR station to purchase a Z6B extension ticket to destinations served by Southern and South-Eastern as well as SWR (or SWT at the time). Was it just a glitch or a deliberate restriction?

 

[paddington]

This seems to happen intermittently, as the same machine sometimes lets you buy it and sometimes says "no fares found" (I think that's the message displayed) at different times.