Dear Paul Filkin
Thank you very much for your helping. The problem was solved as explained below.
I repaired my RENATOCR_Patent Termbase_ENG-US_PORT-BR.sdltb file (99,811,328 bytes, date: December 20, 2018) by producing a New Termbase based on the "RENATOCR_Patent Termbase_ENG-US_PORT-BR_2019.xml" and "RENATOCR_Patent Termbase_ENG-US_PORT-BR_2019.log" files, using Termbase Management Export and Import, and the software EditPad Pro 7 in order to find and replace wrong items on the "RENATOCR_Patent Termbase_ENG-US_PORT-BR_2019.xml" file, before the production of the New Termbase.
Now the "Full Text Search", using the New Repaired Termbase file, in MultiTerm 2019, is working correctly.
Again, thank you very much for your kind attention!
Renato Colonna Rosman