FFMPEG code is not trimming the videos properly

Question

I am trying to trim videos from a specific folder using ffmpeg via powershell but it seems the out doesn't work. However, the files are being renamed as per the code.

<# 

This script trims videos with ffmpeg using a start and end time.
Code below that calls ffmpeg and ffprobe assumes those executables 
are included in the return for $env:path. If this is not the 
case, either add them to PATH or call the .exe using the full
path.

#>

    $files = Get-ChildItem -Filter "*.mp4" -LiteralPath "C:\Users\PC\Desktop\Sample" # create a list of files to process
    $bool_fast = $true # use a fast method to trim the video file. Set to $false to use the slow method.

    ForEach ($f in $files) {
        # set up file names
        $src = $dest = $f.FullName # store original file name
        $new_name = "$($f.BaseName)_LONGER$($f.Extension)" # create a new file name for original file by inserting "_LONGER" before the extension
        Rename-Item -Path $src -NewName $new_name # rename the original file so we can use its name for the output (ffmpeg can't overwrite files)
        $src = $dest.Replace($f.Name, $new_name) # store the new source file name

        # get the file length in seconds
        $strcmd = "ffprobe -v quiet -print_format compact=print_section=0:nokey=1:escape=csv -show_entries format=duration $src" # outputs seconds
        $len = Invoke-Expression $strcmd

        # set start and end times
        $start = 0 # where to start trim in seconds from the beginnning of original video
        $end = 4 # where to end trim in seconds from the beginnning of original video

        # trim the video
        If ($bool_fast) {
            # this method seeks to the nearest i-frame and copies ... fast
            $strcmd = "ffmpeg -i $src -ss $start -to $end -c:v copy -c:a copy $dest"
        } Else {
            # this method re-encodes the file ... slow, but more accurate adherence to a time specification
            $strcmd = "ffmpeg -i $src -ss $start -to $end $dest"
        }
        Invoke-Expression $strcmd
    }