In alpha build 3 when you place a torch down and then start breaking locks around it, the light wont transfer to the new blocks. To get this to occur place a torch down and then break blocks any where around the torch. The light will not transfer to the new blocks. The only was I have found to fix this is break the first torch and place another one. Then the blocks will update and the light will transfer.
MCPE-7763
lighting bug
Resolved
Duplicate
0
This issue has been reported already. It has been linked to the original bugreport.
Please search before reporting any bugs, as it's likely that one exists already.