QFX Import and Reconciled Transactions

[Ramble Winstead]

I recently started using GNUCash at the end of 2017.  I'm very thankful I
found this app.  I'm using version 2.6.19.

For managing my checking account, my main strategy is to simply download
QFX files from my bank and import.  Using this approach, I've found that
pre-entering transactions usually backfires on me since the import fails to
match more often than not.  Not a problem, I've stopped entering
transactions manually, and simply allow the import to handle and for the
most part, the import process works beautifully.  I also reconcile the
account, probably twice a week based on the current balance in my account.

My question/issue is this.  The import process continues to see older
transactions (which have been reconciled), and prompts me to either "Update
and reconcile (auto) match", or "Reconcile (auto) match".  When I allow
those transactions to remain checked and continue the import, the
application has done strange things, such as change amounts, and/or update
the transfer account, which causes issues in future reconciliation attempts.

This is managed easily enough by unchecking these transactions and
continuing with the import.  But, as I mentioned, I started using this
application in late 2017, and I'm concerned that I'm going to be carrying
this burden of unchecking these transactions (and accumulate more), into
the future.

Why would GNU Cash match and attempt to update in any way a transaction
that has already been reconciled?  How can I stop this behavior?

Thank you for your help.

R Winstead