When using the Carleton linefinder tool (which Daniel Nykamp is further developing) following up some lines for stochastic searches I came across loud and broadband coherence in H1:IMC-F_OUT_DQ with CAL-DELTAL_EXTERNAL, see figure 1 (produced by FScan, provided by the linefinder tool).

Andrew Ludgren confirmed the same coherence is also visible with GDS-CALIB_STRAIN_CLEAN and the noise sources was identified as jitter, see: https://ldvw.ligo.caltech.edu/ldvw/view?act=getImg&imgId=361570