once sentinel gets triggered, the only way it can be effective is to kickban *anyone* who does anything remotely flood like. nick changes are one of those things.
People who perform a 'flood' action like nick changes, ctcps to the channel and join-part (i.e. both within a short period) during the flood or during the channel lock will be considered a flooder. As Petersen said, this is required for the script to be effective (at least if you have sl_ban enabled).
In the flood:seconds fields, don't set the seconds part too high, as that will exacerbate the problem in cases where the 'innocent' performs the action prior to the lock.
The next version has a feature that will exempt users who've been on the channel for a set period of time (based on the fact that almost all floodbots join the channel then start flooding within a very short time frame). This will reduce the number of 'innocents' banned.