Command block minecarts disappear .+ forget commads

Hello who reads this. 

I found 2 issues with command block minecarts

Its the same on android and windows  10

For some reason  commands get deleted from minecarts when they go outside render  distance. 

 

And when I reload my world my command minecart despawns altogether ! 

 

I am using them to animate a train i made with blocks  using clone command . The cart keeps copying  the train based on tow coordinates and pasting it above  its location making the illusion that the train is actually moving.