I set separate resistors for each base, it improved the design as it started functioning but the high side transistors were all the time on even with pullup resistors.
I made some modifications and this is what I ended with. What do you think about it? It seems to be working. I do still have a doubt, will it brake the motor when both inputs are high? I don't think so.
By going back to ronv's design, I think that setting both inputs as high would cause a full short and destroy the chips. I hope I'm not wrong once again.