If the objects have different masses, then there isn't a way to start the collision with object 1 moving and object 2 at rest and then end the collision with object 1 at rest and object 2 moving while also having the collision be elastic. You have over-constrained your system, and so you will find contradictions like the one you found here.

If the objects have different masses, then there isn't a way to start the collision with object 1 moving and object 2 at rest and then end the collision with object 1 at rest and object 2 moving while also having the collision be elastic. You have over-constrained your system, and so you will find contradictions like the one you found here.

Using the equations from this answer in one of your linked questions, if we are setting $v_{A,f}=v_{B,i}=0$, then we end up with the system of equations $$0 = \dfrac{m_A - m_B}{m_A+m_B} v_{A,i}$$ $$v_{B,f} = \dfrac{2m_A}{m_A+m_B} v_{A,i}$$

Which you can see is only consistent if $v_{A,i}=v_{B,f}=0$ for $m_A\neq m_B$ (which is the case of no collision), or if $m_A=m_B$.