This is very similar to what I had to go through to recover a few BTC in my old Multibit wallets from 2013 this summer. I had the same problem of underpaying f

This is very similar to what I had to go through to recover a few BTC in my old Multibit wallets from 2013 this summer. I had the same problem of underpaying for the transaction because I had to sweep many small wallets. There are many old wallets around which contain amounts too small to recover. Let's say you have 100 addresses each containing $1, it is no longer economical to sweep them into a single address. Originally in 2011-2013 it was considered a good practice to create many different addresses for receiving.