Here is a new stable build for your servers. It includes lots of fixes and some performance improvements as well as update of the bundled JetBrains tools. Some of the issues fixed can influence the entire server, so update is recommended.
As already usual with bugfix updates, you can upgrade/downgrade within any the 8.1.x TeamCity versions without data format conversions.
Check the upgrade notes and download the build.
We start to switch our main efforts to the development of TeamCity 9.0 with only critical fixes being integrated for 8.1.x versions. The final focus of 9.0 is still in the works, but likely we will work on improving experience of managing large servers and will add some often requested features. If you have any "favorite" direction you would love TeamCity to go into, you are welcome to post your thoughts in the comments.