My VMFXX security is showing big losses but price is stable at $1?

I suggest you go to the Security Detail View for the security in question.  Then scroll through the Transaction History looking for any transactions that show a Price that is not $1.  (You can click on the Price column header to sort the Transaction History so the transactions will be filtered by price....it makes it easier to find where price discrepancies might be.) If you find transactions that show a Price other than $1 you will need to correct the pricing for them. You can double click on those discrepant pricing transactions to bring up the Edit Transaction popup where you can correct the share price.

Did this help you fix the loss issue?

OK.  Being that you are still seeing lots in your account that were sold a long time ago, it's quite possible (probable) that Quicken has entered Placeholders into your register to counterbalance that.  Right below your account register screen, do you to see Placeholder Entries (highlighted in yellow here)?

If so, click on that to see the Placeholders.  Any Placeholders listed will need to be resolved.  Usually resolution means adding, deleting or editing transactions BEFORE the Placeholder date so the shares issue(s ) identified is eliminated.  In your case you already know that you are still seeing lots that were sold long ago so at a minimum you should be seeing one or more Placeholders dealing with that.