  The LHC is undergoing a high luminosity upgrade, which is set to increase the
instantaneous luminosity by at least a factor of five, resulting in a higher
muon flux rate in the forward region, which will overwhelm the current trigger
system of the CMS experiment. The ME0, a gas electron multiplier detector, is
proposed for the Phase-2 Muon System Upgrade to help increase the muon
acceptance and to control the Level 1 muon trigger rate. To lower the
probability of HV discharges, the ME0 was designed with GEM foils that are
segmented on both sides. Initial testing of the ME0 showed substantial
crosstalk between readout sectors. Here, we investigate, characterize, and
quantify the crosstalk in the detector, and estimate the performance of the
chamber as a result of this crosstalk via simulation of the detector dead time,
efficiency loss, and frontend electronics response. The results of crosstalk
via signals produced by applying a square voltage pulse directly on the readout
strips of the detector with a pulser are summarized, and the efficacy of
various mitigation strategies are presented. The crosstalk is a result of
capacitive coupling between the readout strips on the readout board and between
the readout strips and the bottom of GEM3. The crosstalk also generally follows
a pattern where the largest magnitude of crosstalk is within the same azimuthal
readout segment in the detector and in the nearest horizontal segments. The use
of bypass capacitors and larger HV segments successfully reduce the crosstalk:
we observe a maximum decrease of crosstalk in sectors previously experiencing
crosstalk from $(1.66\pm0.03)\%$ to $(1.11\pm0.02)\%$ with all HV segments
connected in parallel on the bottom of GEM3, with an HV low-pass filter, and an
HV divider. These mitigation strategies slightly increase crosstalk
$\big(\hspace{-0.1cm}\lessapprox 0.4\%\big)$ in readout sectors farther away.
