can go into forward always but sometimes wont go into reverse. any solution?

I've gone through a couple transmissions with my old Camry and each time I had the same experience. Talking to a mechanic he said it's typical of Japanese products that when they begin failing they still retain some functionality to get you out of danger, sort of. Your tranmission is telling you it's not long for this world. To replace it will cost a lot of money but if you like the car it's the only answer.

There are servos on most automatic transaxles they will go out from time to time especially if you have a lot of oil leaks. Now... where they are on a camry I have no idea.