Shadowsocks Proxy Poor Performance

[epd5]

Hi all,
I'm running a gluetun container with the shadowsocks proxy enabled, on Docker Engine in Debian 12. I'm finding the performance to be 'spotty', with no obvious signs as to why. Speed tests report anywhere between 50Mbps & 1Mbps randomly, randomly sites will stop resolving & speed tests will report 100kbps-1mbps speeds. This will happen intermittently with no obvious cause .

I'm wondering if my setup is unsupported/unintended. I'm connecting to the proxy from the Shadowsocks (by Max Lv) android app, using the AirVPN DDNS & associated port straight to the app. I'm on a 1Gb fibre line (Speeds around 800Mbps down 80Mbps up, internal network is 1Gbe, Wifi ac) In my mind the rough route it takes to my phone (which I'm wondering is this where the lack of performance stems from?) is then:

If using Mobile internet: My phone -> my mobile provider -> Airvpns servers -> Gluetun -> Gluetun Shadowsocks server -> Gluetun -> Airvpn server -> Out

If using home network: My phone -> My LAN -> Gluetun Shadowsocks -> Gluetun -> Out

I found changing some sysctl.conf parameters around the host kernels buffer memory size really helped increase max reported speedtests from 1.5Mbps to 70Mbps. It however didn't change the intermittent unreliability & website resolving. I haven't been able to gleam any insights from Google/ChatGPT (I guess this is pretty niche).

Could it be to do with Gluetun using the DOT DNS?
Is this an inefficient/unintended setup?
Any other thoughts/pointers would be great. Really enjoying this feature, how it minimizes required configuration for a VPN on my phone.