When deleting a webform which has 1000+ submissions with attachments, not all attachments are deleted. This is probable because of a memory limit or a PHP timeout.
The webform is deleted, so there is no way to properly delete the remaining attachments.
Create we webform with one or more file fields.
Add 1000+ submissions with attachments.
Delete the webform.
Only delete the webform and the related submission when attachments are deleted.
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6.3
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This is probable because of a memory limit or a PHP timeout.
Was there a memory limit or a timeout error logged?
It should probably use a batch to delete the submissions and then delete the form when the submissions are all gone.