Form 8915B was automatically filled out showing taxable IRA is 1/3 of the total. However, the taxable amount shown in 1040 is 1.3333 times the IRA. Can you fix this?

Sounds like you might have entered the IRA distribution twice, once without treating it as a qualified disaster distribution and the other as a qualified disaster distribution that you chose to treat as taxable over three years.  Only the one entered as a qualified disaster distribution will be reported on Form 8915B.  Go back to the Form 1099-R entry section and check for a double entry of the distribution.

Also be aware that the amount on Form 1040 line 4a will be the total amount of IRA distributions in 2018, including any amounts rolled over and the entire amount of the qualified disaster distribution.  Line 4b will show the taxable amount which, in the absence of any other taxable distributions will be the taxable amount determined on Form 8915B.

Thank you for your quick response.  I double checked the 1099R and the amount is only entered once.  The reason I now think this is a Turbotax error is that I had worked on my 2018 return in July and set it aside.  At that time the taxable IRA was correct and showed 1/3 of the total in line 4b.  I made a pdf of the tax return and set it aside.  I restarted working on it in late august, Turbotax made some automatic software updates and then the numbers dramatically changed (i.e. 1 and 1/3 of IRA showing on line 4b), my refund dropped considerably.  The only thing that seems to work is if I delete the 1099R and manually enter the IRA amount in form 8915B.

I would delete the 1099-R, shut the program down, restart your computer then open the program and enter the 1099-R again manually ... see if that helps.

Is this a distribution from an inherited IRA, code 4 in box 7 of the Form 1099-R?

If so, I think I have reproduced the problem you are seeing and I think it was introduced in release R41 on August 1, 2019.  As a workaround, when TurboTax asks, "Did You Inherit the IRA from {payer]?," try answering No.

Yes it is a distribution from an inherited IRA with code 4 in box 7.  Your workaround does work, thanks!  

Thanks for the confirmation.  I've made the moderators here aware of the problem you experienced.

It appears that this has been fixed in release R46.1 on September 5, 2019.  You should again be able to indicate to TurboTax that the distribution is from an inherited IRA.