IRS keep sending similar LTR12C

[kckoo84]

I filed 2021 tax return on April with Turbotax E-file. I owed tax so I paid the owed amount with my e-file.
On Oct. 20th, IRS sent me LTR12C, asking W2, Schedule 1, A ,D. I was not sure why they were asking them since these were in my e-file. However, I faxed those  and the supporting forms with a coverage in their requested format. 
Today, Nov. 15th, IRS sent another LTR12C. Now, they are asking Schedule 1,D and 3. I’ll sent those with supporting documents but I have no idea why they are asking Schedule 1, D again which was both in my original e-file and my response in Oct. I have reviewed sch. 1, D, 3 and found no error. And all supporting forms like Form 8936, 5695, 8949 and even 1099G were in the original e-file and my response in Oct.

Can anybody advise me what this repeating LTR12C really implies ? Does IRS really review it throughly and found error so sending me LTR12C ? I have reviewed my forms multiple times but there is absolutely no error so have no idea what to correct if they are going to ask these again.  Moreover, I paid what I owed, not receiving a refund. Is IRS trying to charge me more ?

[Mike9241]

it could be that the iRS is having issues with its fax system. 

or it could just be that the IRS computers are resending the notice because they are sp backed up its taking it months to get to your response and process it. until then maybe nothing is being entered in it s system that the requested documents have been received.  even though you e-filed there could be something in your return that requires manual processing.  only by calling the iRS could you possibly get an answer but getting through on its phone lines is also an issue 

so you have two other choices

contact IRS Tax Advocate in your state

https://www.taxpayeradvocate.irs.gov/contact-us/#FindlocalTAS 

or use form 911

https://www.irs.gov/pub/irs-pdf/f911.pdf 

or mail the forms to the IRS at the address indicated - use a method where you get proof of delivery