Lower flame of 18k burner is weak

Oven/Range/Cooktop Repair
1

Brand: GE
Model Number: CGS980SEM1SS
Main Symptom: weak burner
What happens & when: cooktop has a high output burner with two rows of flames. The lower row of flame is quite weak.

I’ve taken the burner apart (it is two pieces) WB16T10038 Head Burner Main (Main Gas Burner), 1 Per Pack | Genuine Ge OEM In Stock and there is absolutely no dirt of built up mess between the two parts. It is like new.

I’ve check the gas orifice that feeds the lower row of flames and it is clear and without restriction.

Performance of this burner is lacking

What else could be the problem?

Photo:

flame
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2

If the cooktop is removed, are the gas supply tubes from the valve to the orifice holder in good condition and if the tube for the lower row is carefully removed, does it appear to be clear?