I do not agree this an apparent contradiction between AN 3.47 & SN 15.9 because:
AN 3.47 says all conditioned things having an arising/uprising (uppāda).
SN 15.9 says moving about (samsara) has no imaginable (mata; pp. of maññati) first point (agga).
If we emphasize arising/uprising (uppāda), SN 15.9 is simply saying the first arising/uprising is not imaginable.
However, SN 15.9 may have a contradiction with MN 64 & MN 38, which do point out the first dependent-co-arising (paticca-sam-uppada) of 'satta' ('beings'), when they say:
For a young tender infant lying prone does not even have the notion ‘identity,’ so how could identity view arise in him? Yet the underlying tendency to identity view lies within him. A young tender infant lying prone does not even have the notion ‘beings,’ so how could ill will towards beings arise in him? Yet the underlying tendency to ill will lies within him. (MN 64)
Then, when the child is born, she nourishes it with her own blood; for the mother’s breast-milk is called blood in the Noble One’s Discipline. When he grows up and his faculties mature, the child plays at such games as toy ploughs, tipcat, somersaults, toy windmills, toy measures, toy carts, and a toy bow and arrow. When he grows up and his faculties mature still further, the youth enjoys himself provided and endowed with the five cords of sensual pleasure, with forms cognizable by the eye… sounds cognizable by the ear…odours cognizable by the nose… flavours cognizable by the tongue…tangibles cognizable by the body that are wished for, desired, agreeable and likeable, connected with sensual desire, and provocative of lust. On seeing a form with the eye, he lusts after it if it is pleasing; he dislikes it if it is unpleasing. He abides with mindfulness of the body unestablished, with a limited mind, and he does not understand as it actually is the deliverance of mind and deliverance by wisdom wherein those evil unwholesome states cease without remainder. Engaged as he is in favouring and opposing, whatever feeling he feels—whether pleasant or painful or neither-painful-nor-pleasant—he delights in that feeling, welcomes it, and remains holding to it. As he does so, delight arises in him. Now delight in feelings is clinging. With his clinging as condition, being comes to be; with being as condition, birth; with birth as condition, ageing and death, sorrow, lamentation, pain, grief, and despair come to be. Such is the origin of this whole mass of suffering. (MN 38).
Note: Bhikkhu Bodhi embellishes the above passage in MN 38 by adding the title: "The Continuation of the Round". However, when we read the above passage objectively, the above appears to be about: "The First Point (Agga) of the Round".
Epilogue: It was asked by Yeshe Tenley:
Hmm, so you would not object to someone that said: "Samsara (saṁsāro),
being a conditioned phenomena (saṅkhata), has three characteristics,
Arising (uppādo) is evident, vanishing (vayo) is evident, and change
(aññathatta) while persisting (ṭhita) is evident." Someone could say
the above faultlessly in your estimation?
The term 'samsara' refers to 'moving about continuously'. Therefore, in my opinion, the term 'samara' is not intended to characterise the characteristics of arising, change while continuing & vanishing. The term 'samsara' is intended to characterize moving about without respite & without ending. For example, SN 22.99 says:
"Just as a dog, tied by a leash to a post or stake, keeps running around and circling around that very post or stake; in the same way, an uninstructed, run-of-the-mill person — who has no regard for noble ones, is not well-versed or disciplined in their Dhamma; who has no regard for people of integrity, is not well-versed or disciplined in their Dhamma — assumes form to be the self, or the self as possessing form, or form as in the self, or the self as in form.
"He assumes feeling to be the self...
"He assumes perception to be the self...
"He assumes (mental) fabrications to be the self...
"He assumes consciousness to be the self, or the self as possessing consciousness, or consciousness as in the self, or the self as in
consciousness.
"He keeps running around and circling around that very form... that very feeling... that very perception... those very fabrications...
that very consciousness. He is not set loose from form, not set loose
from feeling... from perception... from fabrications... not set loose
from consciousness. He is not set loose from birth, aging, & death;
from sorrows, lamentations, pains, distresses, & despairs. He is not
set loose, I tell you, from suffering & stress.
Therefore, it is only at the end of SN 15.9, when the vanishing of samara is mentioned, when it is said: "This is quite enough for you to become disillusioned, dispassionate, and freed regarding all conditions".
In conclusion, while 'samsara' is obviously a conditioned phenomena because its arising is dependent upon conditions, the word samsara is only intended to describe its conditioned nature of arising (uppādo) & continuance (ṭhita) but not its conditioned nature of vanishing. In other words, samsara is not Nirvana and Nirvana is not samara. Nirvana is known when samara vanishes. Nirvana is cessation. Samsara is continuance.