I would say dns leak. Does the vpn provider supply you with dns server numbers? I'd put them into your libreelec network settings and use the up.sh script in an earlier post. Use your providers dns settings and not forget to make the script executable. If you can't connect with your providers dns settings, use cloudflares 220.127.116.11 and 18.104.22.168
PS I'd also change the post to not mention bypassing geo restrictions.
In my very limited understanding, wouldn't a DNS leak mean that Astrill wouldn't work in all the cases I've tried, given I am using the same private IP in each case? Whereas, I find it works fine on e.g my laptop, but not when implementing via OpenVPN in Kodi on my media PC