New EB3 I-140 based on past PERM - Receipt Time and Issues

Hello, I’m filing new I-140 with existing EB2 PERM with the same employer.

I believe there are chances that the application may be returned from the mailroom in some cases. Has anyone faced this issue recently? I asked my attorney to include a cover letter to show the application to processing officer before rejecting.

Any how long does it take to get a receipt notice in similar cases? I heard USCIS has to locate the old PERM and it takes a while to get receipt number. Just wondering if it takes couple of weeks or couple of months.

Thanks.