Every shipping label I purchased through Esty send me an additional adjusted shipping charge several weeks after the shipment is completed. I call on everyone and have the shipping adjustments reversed because they are incorrect. Etsy never has a good reason as to why I was charged more than the quoted rate. This needs to change. Does anyone else have this problem?
Etsy is not doing that, it's the post office.
USPS is adjusting the shipping price. Then they bill Etsy. In turn, Etsy bills you.
If you're using UPS or FedEx, they quite often make adjustments after the fact - "surcharges". They bill Etsy, Etsy then bills you.
Perhaps rethink your shipping? (zone, declared dimensions, weight, class of service, etc.)
It's not etsy, it's the whatever service you are using to ship that is billing you the additional amount. The bill just comes to you through etsy.
You are selling large items, how are you shipping them? What shipping company are you using?
It's not Etsy, it is USPS. Read all about USPS's automated package verification program here: https://faq.usps.com/s/article/Automated-Package-Verification-Program
These adjustments can happen anywhere you buy prepaid postage labels. You can dispute them with USPS. It is somewhat easier to do if your buy your labels through PirateShip.
My guess with your inventory is that it is an oversize or over length charge. Are you using calculated shipping? If you are setting your own shipping you need to be aware of those overlength and oversize fees. If you do not account for them in the shipping price you will be left holding the bag.
Knowledge: Parcel Size, Weight & Fee Standards (usps.com)
Your items would be cheaper to ship UPS but even they may charge extra fees after the fact due to delivery location.
Looks like you use free shipping? So are you estimating the shipping yourself? I might ask the PO on drop off if that is enough. There is an overlength fee for 22-30" of $4 and after 30" I think it is $15. Over a cubic foot but under 2 cubic feet is more and it goes up again after 2 cubic feet. Then at a certain size there are "balloon rates".
When I shipped a long package to the furthest zone ( west coast for me) PARCEL was over $90 and Priority was outrageous...like $130+ UPS ground was like $30. It can be a huge difference in price.