The phrase "a series of problematic" is not correct in English.
It is incomplete and lacks a noun to clarify what is problematic. You can use it when discussing multiple issues or challenges, but it needs to be followed by a noun to be grammatically correct.
Example: "The report highlighted a series of problematic behaviors that need to be addressed."
Alternatives: "a series of issues" or "a series of challenges".
It was also by every appearance tucked into a series of problematic tidbits released about Ms. Palin's past, including news that her husband, Todd, was arrested for driving while impaired in 1986.
That confrontation, two weeks before Ms. Schieffelin was fired, was the last "in a series of problematic incidents" involving her, said Emily Nicklin, a partner in Kirkland & Ellis, the Chicago law firm that represents Morgan Stanley.
WASHINGTON — President Obama vowed Monday to "halt the rise of piracy" off the coast of Africa following the dramatic rescue of an American merchant captain, foreshadowing a longer and potentially more treacherous struggle ahead as he weighs a series of problematic options.
This alternative formulation remedies the known systematic underestimations in the classical rating curve and correctly resists the degradation in data quality and availability, as shown in a series of problematic though realistic cases.
Change in the negative appraisals and the trauma memory are prevented by a series of problematic behavioural and cognitive strategies" (Elhers and Clark 2000).
But Hubble had made mistakes — he saw bright patches of gas as stars, for example — and as Dr. Sandage and Dr. Tammann delved into the subject in a series of papers, the problematic constant came down and the imputed age of the universe rose.
Some are comic set pieces, like "Disclaimers," a series of mock-official disavowals of problematic appetites and passions: about "The Rape of the Sabine Women," by Rubens, "the policy of the Museum is not to be taken amiss: / we oppose all forms of harassment".
It had taken the board a year to evict a resident who owned a beagle that barked its head off day and night, and Ms. Payne then worked with board members to take them through a series of tests that could predict problematic behavior.
Also peppering her studiedly fragmented narrative is a series of knock-knock jokes, with the existentially problematic question "Who's there?" Who indeed?
In a series of recent papers, Michael Bratman has embraced the problematic framed by the controversy between Frankfurt and Watson, and has offered a distinctive attempt to answer Velleman's challenge (see, e.g., Bratman, 1997, 2003, 2004, and several of the essays in his 2007 collection).
Although problematic, the LLRC made a series of recommendations to promote peace and reconciliation in Sri Lanka.
