My SOT sent in 3 of my Form 4 applications in mid-November and checks were cashed on 11/23 -- NFA Division says those three are pending as of 11/23.

A fourth Form 4 was sent in the first week of December and the check has not yet been cashed. At what point do I have my SOT send in a new form 4? Further, what happens if the first Form 4 shows up and they process it only to get a second Form 4 for the same can?

This is all fairly new to me, so I appreciate any insight and guidance.

Did you send the form with a tracking number to see if it was delivered?  The checks for Form 4's are being cashed at a serious delay right now.  You may need to wait.

My SOT mailed it and did not use a tracked service, unfortunately.

I'm seeing late January 2021 submissions having their checks cashed, so I would just send another Form 4 packet in.  If they get a dupe, it will be returned for corrections as the s/n is already "in process" in their system.

Thanks, I will do that.