this is realy wierd
i know the issue of gpu lost error ... it seems like you have similar problem at all .... but at 28x at "same time" ?
did you try to use NVSMI? its just monitoring tool for gpu (its easy .bat) ... if this tool writes gpu lost, you can only rma it and HOPE they WILL accept RMA ...
and there is still a problem: i tried to check those bad gpu in common test like Furmark, Heaven Bench, 3D mark (here i need to mention that you need to setup defaults clocks and tdp!!! cz seller can send you to hell when they discover if the gpu was OC and/or under/overvolted) ... all of these programs ran without any error or artefacts ...
the only solution for "subscribing an error" and hope for a positive RMA, was to subscribe as something, they are "unable" to test like:"through AI testing with heavy using of CUDA cores makes an error GPU Lost" and i think you can use it those words for "positive rma" on all cards at once ... this procedure i made about 3 weeks back, waiting for RMA (it will be in another week)
but still check PSUs and check those bad gpus in any pc with furmark etc ... if those cards will makes artefacts or makes similar issues, then rma in common way (but dont forget to change clocks and tdp to default)