Low G string going sharp

Hi. My low G string is really going sharp as I move up the fret board. The rest of the strings are fine. It's only that one string and, at least to my ear, it's quite noticeable. They are Worth Brown strings so they're not inexpensive strings. They're fairly new (around 1 month) and they came on my Cocobolo uke so it's not my lack of stinging skills? Any suggestions on things to check?

I believe this is due to the ukulele being set up for a thin high-G string. Using a thicker string may require saddle compensation. I had this happen with a C string that was thicker than the one the ukulele came with.

An alternative to adjusting the saddle might be to use a wound low-G string. Those aren't much thicker than a high-G string.

Check how the string is fitting into the nut slot. My guess is that it really isn't slotted very well and is riding high above the nut slot. That makes the action of the string high overall leading to the sharp intonation. You can adjust the nut slot by widening it to accommodate or use a wound low g string if you don't want to mess with it.

Assuming this didn't happen with a hi-G. Quite common if the action is too high. That can happen if the nut slot hasn't been opened up for the larger diameter string, or if the saddle was built to support the intonation needs of a smaller diameter G string. My Kamaka HF-3 does this slightly - I've replaced the hi-G with a lo-G but I also opened up the nut to accept the larger diameter. I've replaced nearly every nut/saddle on each of my ukes and will probably do the same on the Kamaka when I replace the strings. Bone is cheap - disgusting smell when worked, though. But it sounds so clear compared to plastics and synthetic bone.