Optimize the internal player.
Other apps and games like temple run and subway surfers lag a lot when a podcast is playing but have no problem while using a external player. Using an external player is not reliable as it doesn't have the necessary options such as sleep timer, 30sec skip etc.

The app uses your device build in player. If you enabled variable playback speed the app will use some CPU for the real time sound processing so other apps requiring a lot of CPU resources might lag. In that case you will have to disable the app audio effects
-
The app uses your device build in player. If you enabled variable playback speed the app will use a lot of CPU for the real time sound processing so it's normal that other apps requiring a lot of CPU resources will lag. In that case you will have to disable the variable playback speed