This seems to become a problem for some, that was created to fix a problem people had https://github.com/LibreELEC/LibreELEC.tv/pull/8161 and added to 11.0.3 not long after https://github.com/LibreELEC/LibreELEC.tv/pull/8180.
I did suffer the same with my remote, but I was able to fix it by using https://kodi.wiki/view/Add-on:Keymap_Editor and mapping the power key to in my case to "suspend".