Ford Focus transmission dilemma

[audriver]

Sorry if this is a HiJack but I'm pulling my hair out with this 2011 Focus we have. Done 103ks service history before us shows its done TCM swap a couple of thousand Ks ago under warranty. I got the car handed to me by my son who parked it up with a trans fault. $1100 later the mechanic claimed it was bad sensors.

I drove it for around 300ks and then again "trans fault" this time different codes and input turbine sensor circuit A fault. So this time I thought, well I'll swap out that sensor for a new one myself. $130 later and 30 minutes later I had it replaced myself and faults gone and driving again.

200ks down the road....she's done it again....same codes.

I was actually prepping it to sell next week, got a RWC, spent $2900 getting it up to sale ready and was looking to pop $5000K on it to recoup something back plus what I have spent. All up with my son and I combined it owes us around $8K still.

My question is.....what would cause this sensor to keep going bad but after 200-300 ks driven each time.

I must admit, when the fault was gone it shifts weirdly anyway but nothing comes back as a code, the TCM is basically new and the clutch packs have been done twice inside 103,000 ks according to service records so what else can be wrong. At this stage I'm thinking I'll have to lose even more money and advertise it as low ks, RWC and rego'd but needs a trans service and sell it for $3K or $4K