Tomtom Start 25 Map screen keeps dropping out to Menu screen

Thanks guys for all your help and suggestions.

I have removed the screen and checked the battery and it looks ok. However I had an old LCD which was cracked and when I swapped it with the screen which was dropping out it never dropped out so it might be the LCD which is faulty and as azzab suggested it may have been on it's way out. I'll see if I can purchase a 2nd hand cheap LCD to test it again as an LCD with a cracked screen isn't guaranteed to give an accurate explanation to the problem.

Thanks again for all your help.