Export-PWDocuments and missing metadata xlsx file


I need to export +90.000 files with excel metadata informations .

I use export-PWDocuments for this (code below)

When i export small number of files, all is OK, i have the right nulmber of files and an excel file with all metadata & audit trail informations.

but when i export lot of files (+90.000), i have the right number of files, the powershell script says that the medatada file has been written...but in fact there is no xls file on my disk.

Copied out 'F:\Export\Suivixxx\171121_Tableau suivixxxxxxxxxxx19\171119 V2.xlsx' (Did not exist on disk)
Wrote 'f:\metadata2.xlsx' OK

Is there a size limit of the xls file ?  a limit of number of documents ?  and why the script says that all is ok if it's not the case ?

extract of script : ( which works like a charm when few files)

$SecurePassword = ConvertTo-SecureString "$($pass)" -AsPlainText -Force;
$cnx=Open-PWConnection -DatasourceName $datasource -UserName 'pwadmin' -Password $SecurePassword -admin -ErrorAction SilentlyContinue

$res=Export-PWDocuments -OutputFolder $DST -ProjectWiseFolder '\xxxxxx_Infra\02-Entrants\Recus\' -ExportVersions
-ExportMetadata -ExportMetadataFile "f:\metadata2.xlsx"
$res | Measure-Object