1- Go to settings
2- To to system.
3- In the system settings, go to storage.
4- The choose, “Internal Shared Storage.”
Note: If you have USB storage go there as well.
5- Now go to “Cached data.”
6- A dialogue will come up saying, “Clear cached data?” Click OK.
Sometimes I’ve had to do this three or four times. Just now, for example, I had 648 MB of cache. First click brought it down to 172. Second click brought it to 68. The third brought it to 18!
Good Luck
@konexions….many thanx 
, works just fine 
I too have the onn 4k Pro it works much better than the new fire stick and much faster. I do not use it connected. I use Wi-Fi only and it works perfect. Try it. I never have no issues with it. I’d like it much better than a fire stick.
I have an old firestick, but I rarely used it it frustrated me more than anything. My fault really, I did not understand the whole using of kodi or I believe Terrarium TV back then. Not sure what drawer it is in currently.
I’ve been having the same problem, but also with my Toshiba Fire TV and my Chromcast.
It turns out the culprit is my internet provider, not any of my devices. I’m in the process of switching from Xfinity/Comcast to GloFiber fiberoptic. Neighbors who have switched tell me their speeds with Ookla and Analiti showed speeds of 25 mbps with Xfinity, over 200 mbps with the fiberoptic.