yes, definitely using spriterdotnet.unity with unity 2017, 2018, and now 2019.4.8f1. So mostly figured it out, I didnt change my code at all, but upgrading to a diff ver of unity did fix that issue. Now if only unity and spritedotnet would play nicely together - same issue as BlooberryPi3 above. Once imported, click any of the prefabs and its a constant jump back and forth between pointer and hourglass, like its constantly searching for any updates in the spriter file, which slows the editor down tremendously. Tested that on 3 different machines here and multiple unity versions, and they all do it.