احسن الله اليكم،والاخوة معكم ودخلكم الله في رحمته،و حبه،و رضاه،و جنته الفردوس Why is a report from sahihayn sahih per default, if in Bukhari nd Muslim respectively there are daef ahadith? Do the3ulamaa' investigate on such hadith(mutfqn alyh),or its said per default as sahih? جَزَاكم اللهُ خَيْرًا

Yes, the scholars of Hadith have agreed across all ages and times that these two books are authentic. While there is a very small percentage that is criticized or subject to discussion, the overwhelming majority of the Hadith are not. To give you an example so that you understand well: if Sahih al-Bukhari has 7,400 Hadith and maybe 30 or 40 are criticized, you can see how extremely small this number is.