what specifically is creeping? I am going to assume mine is 'creeping' :-) - it moves back enough to loosen the chain to a point where the chain starts dropping off every few miles. So basically it is unworkable. In order to tighten it properly I need to remove the crank, loosen the screws on the left and right side of the bracket and use spanner wrench or bottom bracket pliers to rotate the bracket forward again to regain the chain tension, then tighten the left and right screws and reattach the crank. It could technically be done also without removing the crank but the access is somewhat angled and not optimal.
I have had the bike shop work on it and sometimes they tighten it so that the bb only loosens after 500 miles or so but still ... I don't want to deal with that at all.
Just making sure we understand that this is talking about the Rohloff Tandem, not about my Pinion single bike.