4.1 jelly bean – Whatsapp calls get laggy the longer the device is running

On my older Samsung Galaxy Tab 2 (GT-P3100) with Android 4.1.2, which I only use for messaging, both calls and videocalls start to get laggier and laggier the longer the device is running. If I make a call immediately after rebooting the tablet, both audio and video are streamed perfectly to the other device, but, after some time, they start to get worse until the call drops, usually with the message “Call ended because there’s a problem with your phone’s microphone. Try restarting your phone and try again”. Is there something I can do about it?