While rare, this can be caused by several things. First, make sure you are using the correct version of Drumagog. If you have Pro Tools HD, Logic, Digital Performer, or any host that has Plugin Delay Compensation, make sure you are using the Fixed Latency version of Drumagog. Also, if Drumagog's Auto Align is turned on, check the settings on the advanced page and make sure the Align mode is set corretly for the type of drum you're replacing (snare, bass drum). Usually, Psychoacoustic mode works best. In some cases, if the original drum is very different from the sample you're using, auto align mode won't work as well. In these cases, it may be best to turn off Auto Align (a checkbox located on the main page) and manually line up the track by nudging.