The phrase "also not infrequently" is correct and usable in written English.
It can be used to indicate that something happens often, but not all the time, suggesting a frequency that is more than occasional but less than regular.
Example: "The phenomenon is also not infrequently observed in various studies, indicating its relevance in the field."
Alternatives: "also quite often" or "also fairly regularly".
It's sometimes beautiful but also, not infrequently, repulsive, a narcissistic spectacle framed as a liberating vision quest.
Years & Years are also not infrequently compared to Disclosure, and Alexander acknowledges the similarity, but thinks they're really closer to the Pet Shop Boys.
There is also, not infrequently, a twinge of disappointment -- when, say, the invitation to a "Summer barbecue" turns out to be yet another credit card offer.
While Mr. Romney's broad positions on financial regulation, taxes, energy and other issues are shared by other Republican candidates, they have also not infrequently overlapped the interests of his advisers' clients.
"Much of the Polish resistance in its various movements not only failed to help the Jews but was also not infrequently actively involved in persecuting them".
But they're also not infrequently used to identify men who sexually harassed or assaulted women in the decentralized profession, where virtually everyone is a freelancer.
Intermittently adorable, it is also, and not infrequently, tedious (2 30).
They also, and not infrequently, shove them over.
But Jackson's also mentioned, not infrequently, and I think that's correct.
Most trials in early type 1 diabetes have been performed in children, whose remaining β-cell mass is limited, and short-term evaluation of intervention may be difficult also due to not infrequently occurring remission periods (14, 15).
However, these usually life-saving interventions also present those affected with stressful experiences and great demands that not infrequently also trigger consequent psychiatric illnesses.
