In a "Check this Entry" screen, I am asked to enter an amount, but the form does not let me add in the correct value, and clears any value I add.

Is the disallowed loss less than 50 cents? If so, this is a known problem that has been reported to TurboTax, but you can easily eliminate the error yourself.

You can't correct the error in Smart Check, where you get the "Check This Entry" message. You have to go back to where the sale was entered under Investment Income > Stocks, Mutual Funds, Bonds, Other. Edit the sale and delete the wash sale loss amount. In other words, since the wash sale loss is less than 50 cents, you don't report it as a wash sale. An amount that is less than 50 cents would get rounded to zero anyway.