On positive note - even though I have had my share of long and convoluted connections in Frankfurt and occasionally missed a connection due to a late arrival of the first segment, but the other day it worked almost perfectly.

Connecting from a delayed UA944 (ORD-FRA) arriving at gate Z22 to LH126 (FRA-STR) leaving from A22 (bus gate) took exactly 6 minutes including passport control near Z26.
Unfortunately only one of my two suitcases made it to STR with me. The second one was delivered the same afternoon (200km away).

I will not complain about Frankfurt for a while now ;-)