What is the Jarh and Ta'dil (discrediting and accrediting) specific to the narrator Wā'il ibn Mahānah, and is he considered unknown in status (majhūl al-ḥāl), especially since only one hadith has been narrated from him, which contradicts what was narrated by trustworthy narrators?

Ibn Hibban and Al-Dhahabi authenticated Wa'il ibn Muhannah, and Al-Bukhari and Ibn Abi Hatim mentioned him without criticizing him, while Ibn Hajar described him as "acceptable." As for the Marfu' (elevated) hadith you inquired about, its elevation has been established in the Two Sahihs from the narration of Abu Sa'id and Ibn Umar. Wa'il himself elevated it in Sahih Ibn Hibban and Musnad Al-Shashi. Ibn Abd al-Barr favored the narration of elevation over the narration of cessation (mawquf). The statement of one who elevates a hadith is given precedence over one who stops it, provided the one who elevates it is trustworthy.