Welcome to the forum wdasun! In order to help us help you, please consider the following suggestions:
1. Always supply the make/model numbers of the parts in question to help narrow the scope of possibilities. As Mispeld mentioned, firmware info is important with processors especially.
2. Is it the same two/three processors that lose their programs or different ones?
3. Your title states you need help with a PLC5 but your text indicates you need help with ControlLogix. Can you clarify which flavor of processor is failing?
4. Do the failures occur at a certain time (like 4:55pm on Friday) or under similar circumstances (like, whenever we're making recipe XYZ, during a thunderstorm, etc.)