Same problem for me.
Re-opening a project done last month, i got some ‘danger stripes’ in some part of my timeline.
I haven’t move or change the source clips (MXF files coming from a Canon C300. I have tried the replace command, relinking to the same clips without succes.
I have also tried to delete the rendered files to force the refresh without any result.
I am working with a PC, Premiere PRO CC and a collegue has exacly the same problem today with his MAC on another project making us think this is maybe related to a recent Adobe update ?