exp(0) and type conversion in a p-adic extension

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I'm trying to use a $p$-adic extension, and I think I have found two bugs.

The first one: When I try to calculate $exp(0)$, the result is an error instead of 1.

R.<a>=Zq(9,prec=5)
zero=R.zero()
exp(zero)

ValueError: unit part of 0 not defined

The second one happens when I try to convert from R to the base ring. I am using zero in the example, but any value (in the base ring) gives the same problem.

R.<a>=Zq(9,prec=5)
zero=R.zero()
R0=R.base_ring()
R0(zero)

RecursionError: maximum recursion depth exceeded in comparison

I think these are bugs because the operations seem completely valid. This is Sage 10.2.