If you purchased your kit in 2021 summer and your meter is working normally but one (or both) row of 8 LED's seems too dark, then you may have received a bad LM317LZ component for U5 or U6 (or both).
Indeed, we have received a batch of LM317LZ with about 14% of bad parts.
If this is your case, please send us a message on
https://www.soundskulptor.com/en/contact.php and we will send you a new part.
I am sorry for the inconvenience.