Integrated susceptibilities are slightly off for PH channel

The susceptibilities, integrated over tau from the time-displaced correlation function, of the original data and the symmetrized version do not agree, neither for even nor for odd Ltrot step sizes, i.e., independent of beta/2 being on the dtau grid or not. I suspect there is something wrong, either with the symmetrization itself (unlikely), or the dtau weights in the integration, in particular for the points at or close to beta/2.