The new stable version is Tableau Server 2018.2.2. https://www.tableau.com/downloads/server/pc64
and Yes there are a lot of issues because the upgrading has a special way of upgrading.
You can try to check my posts about upgrading with step by step procedure.
This is similar to upgrading from 10.x to 2018.x.
Please mark this if it helps you or correct answer.
2018.1 is VERY different than 2018.2! Do not be confused by the "2018" version name.
The easier upgrade would be to 2018.1.x. This gets your users to a good, modern version with minimal fuss on your end and gives you time to then grab a QA Server and try to install 2018.2.x...and please use the newest version of 2018.2 that is available!