To clarify, not multisite, but two separate sites on two separate domains on the same VPS.
At first, I had both sites installed with w3tc. Later on, I updated them with wpredis and content on both sites got mixed up. Even some of the backend settings got mixed up. IE: content from site1 appeared on site2 and vice-versa
If it makes any difference: both sites run on php7 with let’s encrypt on Ubuntu 16.04. All plugins and the VPS itself is constantly kept updated. Latest EE version too.