The way the LWS is operated means that the spectra for different detectors will have an overlap region. Although these overlap regions of sub-spectra should after the processing be at the same flux level, it is known that in some cases there is a difference between the subspectra. These differences can be due to imperfect correction for the spectral response changes during the AOT, or to problems with the absolute flux calibration. It is expected that the in-orbit calibration solves many of these problems, but it is also inevitable that some differences will remain. It has become clear that especially the LW1 detector does not line up correctly with the other detectors when a faint source (like a galaxy) is observed. In that case the absolute flux level of the LW1 detector should not be trusted (the relative response calibration, i.e. within the detector, should be OK). Currently this effect is under investigation. An indication for a way to fit the spectra back together is given in section 10.5.