Without further ado, if you did experience this kind of problem, just revert your version of WhatsApp back to the (more stable) previous version available in Nokia Store (WhatsApp 2.8.22).
To do this, firstly you have to uninstall the later version, which is 2.8.29 in my case. Be notice that by doing this, it can erase the conversation history, so make sure you have backed up the important message(s). After that, go to the Store, then download & install the 2.8.22 version of WhatsApp which is available there.
InsyaAllah the “Paste” function will recover.
[EDIT] The latest WhatsApp 2.8.3 insyaAllah will not have this “Copy and Paste” problem anymore. Yesterday I tried it myself and the problem didn’t occur.