Quantum spin Hall devices with edges much longer than several microns do not display ballistic transport; that is, their measured conductances are much less thanﾠe2/hﾠper edge. We imaged edge currents inﾠInAs/GaSbﾠquantum wells with long edges and determined an effective edge resistance. Surprisingly, although the effective edge resistance is much greater thanﾠh/e2, it is independent of temperature up to 30ﾠK within experimental resolution. Known candidate scattering mechanisms do not explain our observation of an effective edge resistance that is large yet temperature independent.