Your GPU 5 overclocking/undervolting is probaly not right .
each card need to be fine tuned separetly for the best performance.
Your GPU 5 might have a lower ASIC quality , try to leave gpu 5 on the factory/default settings , and tuned the card step by step slowly till you can find GPU5 "sweet spot"
Do you have a monitor connected or a dummy plug to GPU5 ?
ohhh that can happen without any overclocking/undevolting, all that needs to be is the PSU not having enough power to power all gpus while mining. I'm having the same issue with my rx 580 rig and a 1200w psu, always 1 gpu and usually its the 6th one that stays at 0 sol/s, that said you might wanna try a bit higher wattage psu if you don't plan on modifying the bios settings. so funny how you noobs always seem to overlook the most simplest things. also btw the way if your going to come on here asking question such as the one you've asked, it would be wise for you to post your hardware spec's so everyone that responds could give a better educated answer instead of playing the guessing game with you like some noob fool
