I have been a customer of yours in the past and spoken to many of your customer over the years about the overall wait times to get guns to their local in-State dealers.
Ironically I was actually talking to one of your less than pleased customers yesterday who is waiting on an "extended" time period Form 4 approval to MWT.
In that discussion yesterday I listed many of these issues you described above that are outside of your control. I mentioned that many of these are probably estate guns, I bet there are correction letters because models and lengths are all messed up from the last transfer in 1989, and you have old people and non-gun people on the other end of the transfer trying to deal with this. Your "seller" is statistically probably an 80 year old widow whose husband is now deceased and she may be dealing with a bunch of different estate issues, not to mention the loss of her husband, and getting a scary looking correction letter from the ATF, demanding her get the gun out and take pictures with a ruler using her jitterbug phone and its just is a mess to deal with. USPS loses stuff both inbound and outbound. Form 4s get misplaced tucked inside a paper TV Guide she still receives in the mail and isn't found until she is looking up when that Matlock rerun comes on, etc.
However, I can offer some advice in your business model that may help here based off my personal experience as well as that of others I personally know who have bought dozens of guns from you all over the year.
You need to be more transparent with your buyers on the time these paper Individual Seller to MWT Form 4 transfers take and the overall time it takes to get to the gun to their dealer.
Telling buyers that Form 4s come back in "30 to 45 days", or that is should be here "soon" or "any day now", etc. just misleads them and makes them angry and come post here when it doesn't happen that way.
Sure maybe some of them do come back in a month.....but not all of them. Some of these paper F4s to dealers take 6 months or more just to be approved.
On top of that, just because the Form 4 is approved doesn't mean that the seller magically get the approved paper form Form 4 in the mail that day and ships the gun to you pronto. Quite often, it takes up to another month for the approved paper Form 4 to be delivered to the seller and they then have to pack up and ship you the gun. God help you if that paper Form 4 is lost in the mail...as now you are waiting 45 days before the ATF will even accept a certified copy request and then its another month once a certified copy request is submitted and gets back to the seller. In that scenario you could have two months or more just waiting to get a copy of the Form 4 for the seller so they can ship the gun. That's on top of the 6 months the Form 4 approval potentially took.
The buddy I talked to yesterday about his extended wait time, I told him once MWT asks for the balance payment (once it shows up in MWTs eForms inventory) set your expectations on 2ish month before the gun gets to your dealer. The seller is going to have to wait for the paper Form 4 to arrive (up to 30 day), pack and ship the gun (another week or more), MWT will have to intake the gun and then repack it and reship it to his dealer (say another week or so). If it all goes swimmingly its maybe 4 weeks to arrive your dealer. Shit goes sideways and USPS loses the approved Form 4... or some other delay than plan on a couple months or more after you pay the balance.
You need to give sellers a date the Form 4 went pending with the ATF (meaning it cleared the Oregon bank PO box hurdles) and be very clear that these are paper transactions, that use USPS as the carrier pigeon, and the person on the other end of this transaction may be an 80 year old widow who doesn't know a tape measure from a hammer or an estate attorney who know nothing about machineguns and are slow to mitigate problems that may crop up. Due to all these factor these Form 4 transfers to MWT can potentially take upwards of 9 months to complete and get the gun to their dealer.
When people ask me how long does a Form 4 to a dealer take time wise I tell them on average plan for 2 to 9 months in most cases and some small percentage fall outside that range. (a buddy of mine just had one take almost two years with corrections)
I know you all are trying to be "efficient" with some of your strategy here but the government doesn't work that way. This is the same government that processes former employee separation papers in an underground mine using reams of paper, wheeled carts and a single elevator to move it all around.
Sending in a single payment for multiple transfers is asking for problems. Sending in one set of estate docs for multiple transactions is again asking for problems. Limit the unforced errors on your side even if it means killing a bunch of trees in the process.
Its the same deal when I submit 5320.20s for temp moves to a shoot out of State. Sure you can put multiple guns on one form. You know what happens if you do that and they don't like the model name for one gun....all three get disapproved. I always put one gun on one 5320.20. Same with fingerprint cards , checks for tax payments, trust or supporting docs. Can you get away with sending in a single set...sure .sometimes it all goes to plan with one set of docs, payments, etc. What limits the odds of failure, sending in each application to stand on its own merits. I send every application in its own envelope or separate email to NFAFax to maximize my odds because postage and emails are cheap and government employees including the postal service are not great.
Again if you are running a business and don't want complaints here about extended wait times put the odds in your favor. Every application you submit needs to stand on its own so when some government employee in WV. or OR. splits up the applications everything else in that batch doesn't end up denied because you were trying to be efficient.
I am not posting this to beat you all up and I actually recommend folks buy guns from MWT. However that recommendations always comes with the caveat about the realistic time its going to take for an "incoming" gun they buy to actually get to their dealer. This is especially critical in the days of 24 hour eForm 4 approvals and folks who don't understand the time difference a paper Form 4 takes.
Just my two cents anyway.