GPI shows all my aggregated files as blocking render and I'm on VPS

I use the module for at least a year and half and it greatly helped me to raise GPI score in my sites, as always I am thankful for you amazing work.

Configuration:

- Use DNS Prefetch for external CSS/JS: Enabled, below charset=utf-8 (recommended).
- AdvAgg Cache Settings: Normal ~ 60ms.
- Obscure Options: Convert absolute paths to be protocol relative paths.
- CSS Options: Combine CSS files by using media queries. && Fix improperly set type.
- Bundler - active: css bundles - 4 | js bundles - 4. && Grouping logic = File count.
- css compression: YUI
- Moved all JS to the footer.

Environment:

I recently moved to a VPS (Digital Ocean, common 20$ plan) and have 3 minimal, almost all-core sites (2 Drupal 8, 1 Wordpress).

My theme Is a a CSS-only customized Bartik and since moving to VPS (Ubuntu 16.04, Apache 2.4, lightweight system) I encounter the GPI score of 63/87 (mobile-desktop) even after enabling seemingly all my Advagg aggregated files appear in GPI as "render blocking". The only way I could explain this is the fact I've yet to enable mod_deflate to have Gzip compression (I've already enabled mod_headers && mod_expires and ensured it's working).

While I need to learn some more before enabling mod_deflate, I wonder if there is anything else worth checking in Drupal-Advagg relations.

Note:

This error I encounter in about of 50% GPI tests might be associated (it happens only since I moved to a VPS but never happened to me in a shared server).