Stimulus check payment wrongly entered as a child credit tax by Turbo Tax

It is not a glitch -- it is your own user error.   If you received the 3rd EIP payment  as shown on letter 6475 you were supposed to enter that information in Federal Review for the recovery rebate credit--not on form 8812.   

Letter 6419 shows advance child tax credit payments which you enter on form 8812.

No, there isn't an issue please follow these steps to enter your advanced Child Tax Credit received:

 Click on the "Search" on the top and type "Child tax credit"

1. Click on “Jump to Child Tax Credit” 
2. Continue through the questions until the "Tell us about any advance Child Tax Credit payments" screen and enter the advance payment amount from letter 6914.
3. Continue through the questions.

You can see your remaining Child Tax Care Credit amount on line 28 of Form 1040. 

To preview your Form 1040:

1. Click on "Tax Tools" in the left menu
2. Click "Tools"
3. Click "View Tax Summary" in the Tool Center window
4. Click on "Preview my 1040" on the left

Please see What is the Child Tax Credit? and IRS 2021 Child Tax Credit and Advance Child Tax Credit Payments FAQ for additional information.

To verify/enter your third stimulus payment received:

1. After entering all your information click "Search" at the top right and type "Stimulus".
2.  Follow the jump to link (if you do not qualify for the Recovery Rebate Credit the stimulus questions will not come up). 
3. On the screen "Let's double-check the amount you received" you will be asked about the amount of third stimulus payment you received. TurboTax will then calculate the amount of stimulus payment remaining that you are still entitled to get.  
4. Any stimulus amount remaining due to you will show as The Recovery Rebate Credit on line 30 of Form 1040.

Please see What are the eligibility rules for the Recovery Rebate Credit? for additional information.