Cyclic csv-Import to SQL file by file - sql

Question

I try to write a short script that cyclic imports csv-files to a SQL data table that are being dropped in an import folder ($sourceSQL). Each csv-file consists of one line of information (here three columns). To make sure that the file was successfully written to the data table, I check if the unique Id can be found in the table.
So far it works with the first file. However, the second file gets only moved to the destination folder without being written to the data table. I can't find the problem. Is it because of the $data variable?
$StartButton.Add_Click({
$script:ActiveLoop = $true
while ($script:ActiveLoop){
If (Test-Path $sourceSQL){
$data = $null
Do{
$data = import-csv $impcsv -Header A,B,C
foreach($i in $data)
{
$Id = $i.A
$State = $i.B
$Sequence = $i.C
$query = INSERT INTO $SQLTable (Id, State, Sequence)
VALUES ('$Id','$State','$Sequence')"
$impcsv = invoke-sqlcmd -Database $SQLDatabase -Query $query -serverinstance $SQLInstance -Username $SQLUsername -Password $SQLPassword}
$SqlQueryId = "SELECT TOP 1 Id from $SQLTable ORDER BY Id DESC"
$SqlConnection = New-Object System.Data.SqlClient.SqlConnection
$SqlConnection.ConnectionString = "Server = $SQLInstance; Database = $SQLDatabase; User ID = $SQLUsername; Password = $SQLPassword"
$SqlCmd = New-Object System.Data.SqlClient.SqlCommand
$SqlCmd.CommandText = $SqlQueryId
$SqlCmd.Connection = $SqlConnection
$SqlConnection.Open()
$IdCheck= [string]$SqlCmd.ExecuteScalar()
$SqlConnection.Close()
} Until ($Id -eq $IdCheck)
Move-Item $sourceSQL -Destination $destinationSQL
}
[System.Windows.Forms.Application]::DoEvents()
}
})
$objForm.Controls.Add($StartButton)