Updating report viewer 2016 problem
Also, sometimes when you change parameter values IE11 stops responding or it takes a long time to load the report.You may also find that the toolbar that displays the report controls and export features, appears on multiple lines when viewed with IE11.Turns out they weren't actually having an issue with the print button or anything (as described in my original link), so it is unclear whether it was really the same issue at all.
The v12 report viewer is backwards compatible with 2005, 2008, 2010 and of course the 2012 schema definitions (which is used by the 2014/2015 report designers).
Virtually all discussion I can find of this problem refers to this article (or to a now-unavailable MS Connect page).
The problem is that the server-side fix suggested for SSRS 2008 doesn't work for SSRS 2017 (there is no tag to this or a different ASPX file?
When you preview the same SSRS report in Chrome or Mozilla Firefox, it works fine without any issue, which means it is a browser compatibility issue.
How can you make SQL Server Reporting Services (SSRS) compatible with IE11?