My aged mum -in-law left her 5 year old 4000 mile Fiesta standing outside for a year and then gifted the car to my wife

. After the local garage jump started it the speedo failed to work and we were told by the local Ford dealer that a new dashboard would be necessary

. This was replaced and worked ok for a few months and then went again

and was replaced again but under gaurantee

. After another 6 months it has gone yet again

. The dealer is unable to find the underlying cause of the problem and now we are expected to fork out ££££'s to replace it yet again when it will almost certainly happen again.
Is this a unique case or what? Can anyone suggest what is going on?