Reinforcement Learning model always gives different output
Reinforcement learning in principle should not be the source of stochasiticy, i.e. given exactly the same inputs the dqn model and the rl agent should give exactly the same output.
The source of stochasticity in your setting may be the random seed. Make sure to set it once and share it with all libraries
that have a stochastic aspect (i.e. network initialization, batch selection, your simulator if you are using one).