Dual 5700 XT issues

Hi all i setup a mining rig with dual 5700xt mech oc with original bios and no mods except thermal pads modded them both sides since amd doesnt cover both sides to lower temps/ temps hover at 60c for gpu and junction temps with an undervolt to 925mv (130w) 1300mhz clock with a mild oc of memory to 1812mhz up from 1750 stock very very stable but after say 5 minutes the power on the second gpu drops from 130w to 70w but if i stick it in another pc it works fine or if it leave it by itself in the same pc it works fine only when i have 2 the second one drops. Changing slots didnt work, setting gen 3 or 4 for pci e doesnt help in bios try changing wires for power didnt help tried a 1250W thermaltake power supply didnt work. Im using windows 10 1809 LTSC with the latest software from amd and driver. Asus Hero Wifi X570 with 3600X Stock with 16GB 2666 memory 1600W T2 EVGA Power supply that is brand new straight from factory. Any ideas? ive searched all over the internet havent encountered similiar issues to other ppl. if you know someone who might be helpful recommend them here please any help is appreciated, Pheonix miner 5.5c is what i use on betterhash @Mr. Fox @Papusan @S.K