What Are Your Flawed Masterpieces?

What is a series that you both love and hate? A series where the high points are just amazing for you, but there are low points (bad plot-line, character arc, writing choice) that really bring it down.

For me, two series fit that description:

1) Memory, Sorrow, and Thorn - some of the best world-building and battles I’ve ever read. (And the stuff with the elves is my favorite elf stuff I’ve ever read) BUT, some sections are a horrible slog, some characters horribly annoying/boring, and an ending that really felt like it didn’t live up to the buildup.

2) Realm of the Elderlings - Immaculate prose, amazing companion in Nighteyes, and some stellar character work. BUT, several books are kind of meh, lots of pacing issues, some frustrating plot-lines, and many plot-lines that seem to exist only for the sake of misery-porn.

Of course this is all subjective. I would love to hear what series, for you, is so close to being perfect/amazing, but just misses the mark with a couple flaws?