the fixed seed will not solve your problem, because different functions are called for different simulation parameters and thus the random generator yields different results.
You can use the option LTE_config.UE_distribution = ‘predefined’ for the user distribution. You only have to specify x- and y-coordinates of as how many users you want to place and they will be at fixed positions no matter the simulation setup.
If you want to take advantage of the UE distribution functions, you can also create the UE cache once (e.g., for a simulation without RRHs), and save it under an arbitrary name (not the automatically generated one). This name you then use as LTE_config.UE_cache = ‘my_cache’ and load it for the next simulation (e.g., when using RRHs).