Try:
p= next_prime(1000) # or some other prime
R.<x,y>= GF(p)[]
pol= 18*x
print(pol/x)
When $p$ is small, this correctly prints 18. However, when p is at least 536870923 (the first prime after $2^{29}$), this prints 18*x/x, the fraction is not simplified.
I'm on sage 10.8 installed this morning.
