If you are using a User motion file (.umt file) that has been downloaded from SimROUTE it is important that the integrity of the file is not changed in any way as this will lead to a checksum error when the scenario uses the motion file.
Of particular note is the fact that the filename, entered in to SimROUTE when the .umt file is generated (see extract below), is taken into account when the checksum is calculated. The checksum information is appended to the end of the file. Once the .umt file has been downloaded it should be saved to the relevant scenario folder without changing its filename or its content.