The phrase "again a challenge" is correct and usable in written English.
It can be used when referring to a situation or task that has presented difficulties previously and is doing so once more.
Example: "This project has proven to be again a challenge, just like the last one we tackled."
Alternatives: "once more a challenge" or "yet another challenge".
"It was always a challenge to play against him and again a challenge that I'm looking forward to".
Mr. Cheney was the last Republican secretary of defense, serving under Mr. Bush's father, President George Bush, and had a very clear idea of the ideal candidate for the job: qualifications that Mr. Rumsfeld fit to a T. The only trick was persuading Mr. Rumsfeld to serve again, a challenge that Mr. Cheney took on over the past several days, transition aides said.
"It's really, yet again, a challenge to the internet industry to help us all do more to stamp out these terrible crimes".
Sevastova again wins a challenge.
Second serve again, and a challenge from Djokovic - which he loses.
A second and more controversial penalty in the 23rd minute was again for a challenge on Defoe, this time by right-back Paul McGinn.
But you can see the way in which the modern city rings the site, and again what a challenge it would be to remove that modern city and to reveal the rest of Herculaneum.
With a conservative majority back in place, the Supreme Court on Thursday announced that it will once again hear a challenge to the required payment of fees to public-employee unions, an important but controversial tool for the American labor movement.
These differences again offer a challenge to a rational explanation.
Back in February the court judged that data-sharing activities between the NSA and GCHQ had breached European Human Rights law, again after a challenge by civil rights groups.
Just getting to like myself again was a challenge.
