Like fdb said, it should be 'profitentes' instead of 'profites'.
Nicolaus Cusanus cited Ketton's translation like this: "Profitentes etiam se suae caedis authores cordibus suis non minimam ambiguitatem inde gerunt, [sed eum nullatenus interfecerunt]" (https://books.google.nl/books?id=mQ-KDwAAQBAJ&pg=PA46).
Translation by Hagemann and Glei: "Selbst wenn sie sich als Anstifter seiner Ermordung erkennen, haben sie in ihren Herzen nicht geringe Zweifel; [getötet jedoch haben sie ihn keineswegs.]"
Note also that 'non minimam ambiguitatem' is not translated as 'not the least/smallest bit of doubt', but rather as 'not (very) little/small doubt', i.e. litotically: 'considerable doubt'. A Google search for 'non minimam' seems to confirm that it tends to mean the same as 'non parvam'.
So it would be: "Even when declaring themselves to be the instigators of his murder, they have no little doubt in their hearts about it; [yet by no means did they kill him.]"
This is an adequate paraphrase or summary of the Arabic:
وَإِنَّ ٱلَّذِينَ ٱخۡتَلَفُواْ فِيهِ لَفِى شَكٍّ۬ مِّنۡهُۚ مَا لَهُم بِهِۦ مِنۡ عِلۡمٍ إِلَّا ٱتِّبَاعَ ٱلظَّنِّۚ [وَمَا قَتَلُوهُ يَقِينَۢا]
Which in Marracci's more literal Latin is translated: "& profectò qui discordes fuerunt circa eum; esset ne ipse, an alius similis ipsi; certè fuerunt in dubitatione de hoc (de vera morte ejus) non fuit illis de hoc ulla scientia, sed tantùm sectatio opinionis. [Et non occiderunt eum verè]" (https://books.google.nl/books?id=IQdRAAAAcAAJ&pg=RA1-PA171, under verse 156).
So the Quran's "وَإِنَّ ٱلَّذِينَ ٱخۡتَلَفُواْ فِيهِ" ("and indeed those who differ in this matter/concerning him") and Marracci's "& profectò qui discordes fuerunt circa eum" correspond to Ketton's "Profitentes etiam se suae caedis authores".