I just designed a pcb with EasyEDA then i realized that i forgot a track connection. When i try to connect the component pins, it does not connect to an existing track. They are not locked. I showed the issue with a circle highlight above...
Could you suggest anything? or is this a bug?
Brand new interactions and interfaces. 
Easy to use and quick to get started. 
Your net names are different.
The correct way to do this is to update the schematic first and then do Update PCB... or Import Changes... to pull the changes into the PCB.
Then you can reroute without errors.
Please read (2) in:
https://easyeda.com/forum/topic/How-to-ask-for-help-and-get-an-answer-71b17a40d15442349eaecbfae083e46a