Kodi will not stay uninstalled

Hi all, and thank you for reading my post

I recently purchased a mini A5X_plus android 8.1.0 tv box
box came with Kodi Version 18.0-BETA3 (thats all it says in the app section of settings)
now this version of Kodi will not open up and will not stay deleted
I've done several things to try to delete Version 18.0-BETA3 without any success
I have deleted this version, downloaded Kodi 17.6 and Kodi 18.0 Alpha1
now I have no problems at all with 17.6 and 18.0 Alpha, all works great until the electric supply is switched off
then when my box comes back on Kodi as reverted back to 18.0-BETA3 and this version will not open

any ideas on how in can fix/delete this please

thank you all in advanced

John