This is what happens with the Earth's excess angular velocity (momentum) over time
Note the strong hiccup ~1983 where it appeared the earth's rotation slowed down temporarily.
That coincides with the point that the SOI model also loses coherence with the underling data.
This is a prior analysis:
Chao, Benjamin Fong, and Isao Naito. "Wavelet analysis provides a new tool for studying Earth's rotation." Eos, Transactions American Geophysical Union 76.16 (1995): 161-165.
Like they say, what is confusing is the QBO has the opposite polarity when comparing the two events.