This has been an issue reported by a number of users.
Make sure your version is up-to-date as TT is constantly making updates. Supposedly it is fixed, but no promises.
See the response below from a TT lounge discussion thread:
If a charitable donation of cash is entered on Schedule A the program still comes up with an error for the entry of $300 on the 1040 Line 12b when filing as Married Filing Jointly but entering $600 corrects the problem and the error does not re-occur unless you go back and add data to the federal return, then in Final Review the error pops up again. Correcting to $600 fixes the problem again.
*A reminder that posts in a forum such as this do not constitute tax advice.
Also keep in mind the date of replies, as tax law changes.
