FEP based analysis techniques may be unreliable if neighbouring states do not have overlap in the sampled energy distributions. From the 324 relative binding free energy calculations performed in this work, one was identified as having a low overlap: this was l12-l35 in the MCL1 target. However, this low overlap was not found to translate into a difference in the TI and FEP results. Low overlap was found more frequently if analysis was made for "one-off" simulations but averaging over many replicas eliminated this in all but the one MCL1 case.