Must one repeat the Tashahhud from the beginning when in doubt about completing a part of it, or can one complete what was missed?

If someone doubts having omitted one or more words from the Tashahhud, they should recite what they doubted omitting and what comes after it. They are not required to return to the beginning of the Tashahhud. However, if their doubts become frequent, to the point of occurring daily, they should disregard them and not act upon what they doubt. One must be wary of pursuing obsessive thoughts.