MD restart with duplicated frames

Hi, I'm trying to continue/restart my MD in ASE. The problem is, after I pass the trajectory (in str) to the MD object, I have found that the last frame of the previous traje gets calculated again and appended into the new MD trajectory. Which basically means if I use the built-in append trajectory method, I will get two duplicated frames And the MD object does not take in a sliced trajectory since that wil be of TrajectoryReader class that is not writable.

Is there any work around to continue a MD from a trajectory?