Hello Shelby,
The issue that you are reporting about storage getting filled up is a common problem and a lot of users did already report this.
It is when your memory is getting filled up with temporary files (cache files). To correct that out please follow the procedure below:
1: Start your box as normal.
2: Then Click on Circle with 6 dots at the Bottom of Screen, it will open up your apps.
3: Then Click On Es File Explorer.
4: The on left hand side menu in Es File Explorer click on Tools
5: Then Click on Sd Card Analyst
6: It will analyze the memory of your box and display which folder is taking up the maximum space.
7: Then click on the top most folder which is the folder taking max space on the box which will usually be Android.
8: Then Click on Data folder>then click on org.xbmc.kodi or com.semperpax.spmc (if using DBMC) then Click on Files then Kodi or Spmc (if using DBMC) then you will see the temp folder.
9: Delete if you see temp folder by selecting and long press the OK button which will bring a tick check mark on the right side of the folder and a Delete option will now be visible near the bottom of the screen
10: Hit the Delete option then go back to the Home Screen. and restart your device... Then again go back into DBMC load wookie retro pack or new look wookie skin if you are using DBMC.
11: After loading wookie on it go onto System option inside XBMC or DBMC and then from Drop down on System go into Xunity Maintenance>Tweaks> Click on 0 Cache Advanced XML
(0 cache advanced xml will prevent storage of cache files (temp) on the device)
That should resolve the issue.
If it does't resolve the issue then please follow the video given in below link:
Hope that helps you out...