Instinct solar losing time and miscalculating distance

Hi

My watch is two years old and has been used intensely so I realise this could just be a question of the watch getting old.

As soon as I finish a ride and the gps is disconnected the watch starts to lose time. After one night about half an hour.

Also miscalculating distance. About 10 kms for every 100 kms cycled in comparison to my komoot navigation app.

Until this started happening they were always pretty much the same.

I have updated all firmware and factory reset. Nothing has helped.

Any ideas greatly appreciated.

Thanks Tom