Repeating Commands with Always active Are Broken!

If you use a repeating commandblock and turn it on always active it stops working after a few mins or hours! So if you do some commandblock you can just play a few hours with it and then you have to rewrite them again! However if I copy the block with Control and the middle button on my mouse and I place the commandblock down its not working. But If I write the command again with the same settings this command is working! Its completely stupid... I hope you can fix this bug! O_o
With kind regards Matthias!