"unclear reason" is a correct and usable phrase in written English.
It can be used when you want to describe something that does not have a well-defined cause or explanation. For example: "She left without saying a word, so we were left with an unclear reason for her departure."
Notable is instance C which yielded a significant range of performance variation, again for an unclear reason.
Solubility test results showed that the synthesized copolymer link is sparingly soluble in solvents tested, and also electrical conductivity of grafted copolymer is less than Ani with unclear reason.
Solubility test results showed that the synthesized copolymer link is sparingly soluble in solvents tested; also, the electrical conductivity of the grafted copolymer is less than the Ani with unclear reason.
He served in the group as a security officer, martial arts instructor, and student minister before leaving for an unclear reason in 1963.
An Arizona police officer threatened an immigrant with death if he moved after his car was stopped for an unclear reason, a video uploaded to YouTube by an immigrant rights activist appears to show.
For unclear reason, Brock contends, she was taken into custody and transported to the NYPD's 30th Precinct, where she was held for a few hours before being released without being charged with any crime.
Uber, for unclear reasons, included the so-called "Paga waiver" anyway.
A government board disqualified several serious would-be contenders for unclear reasons.
For unclear reasons, her parents and those of her friends are going insane.
Three Saudi diplomats were killed in Bangkok at about the same time, for unclear reasons.
For tantalisingly unclear reasons, Mrs C has hired Marlowe to find a former lover, Nico Peterson, who has disappeared.
