What does this SkeletonAnimation error mean?

I have been trying to solve this error for a while now but I am not sure what may be causing it. It seems to have popped out of nowhere after I created several actors with the same plugin and animation file. Any help would be appreciated, thanks gzserver: /var/lib/jenkins/workspace/gazebo8-debbuilder/build/gazebo-8.5.0/gazebo/common/SkeletonAnimation.cc:147: ignition::math::Matrix4d gazebo::common::NodeAnimation::FrameAt(double, bool) const: Assertion `(t >= 0.0 && t <= 1.0)&&("t is not in the range 0.0..1.0")' failed. My world file model://sunmodel://ground_plane-1 1 0.5 0 0 0moonwalk.daewalk.daetruestand.daetrue1.15humanone1.85.1ground_plane-1 2 0.5 0 0 0moonwalk.daewalk.daetruestand.daetrue1.15humantwo1.85.1ground_plane EDIT: I managed to find what is triggering my error although I am not sure why that is so. I am using an edited version of the Actor plugin provided in the tutorials (https://bitbucket.org/osrf/gazebo/raw/default/plugins/ActorPlugin.cc). For some reason changing the following in HandleObstacles removes the error. if (std::find(this->ignoreModels.begin(), this->ignoreModels.end(), model->GetName()) == this->ignoreModels.end()) { to (added ! before std) if (!(std::find(this->ignoreModels.begin(), this->ignoreModels.end(), model->GetName()) == this->ignoreModels.end())) { EDIT: After further investigation, I managed to pin the line causing this error when the equality signs change in the if statement. It is due to the following two lines _pos.X() -= offset.X(); _pos.Y() -= offset.Y(); in this function void ActorPlugin::HandleObstacles(ignition::math::Vector3d &_pos) { for (unsigned int i = 0; i < this->world->ModelCount(); ++i) { physics::ModelPtr model = this->world->ModelByIndex(i); // Do not handle the target to follow as an obstacle. Follow buffer should keep a safe distance. if(this->mode == "follow" && model->GetName() == this->targetName) continue; if ((std::find(this->ignoreModels.begin(), this->ignoreModels.end(), model->GetName()) != this->ignoreModels.end())) { ignition::math::Vector3d offset = model->WorldPose().Pos() - this->actor->WorldPose().Pos(); double modelDist = offset.Length(); if (modelDist < 4.0) { double invModelDist = this->obstacleWeight / modelDist; offset.Normalize(); offset *= invModelDist; // Only change the X and Y direction vector components... Unless humans can levitate in the future... That would be cool. _pos.X() -= offset.X(); _pos.Y() -= offset.Y(); } } } } However, I am still unsure why this is happening?