Heimerdinger has multiple new bugs this patch!
As seen by the video posted by JaymaicanGames on reddit Heimerdinger has several new bugs. RW and W are counted as different spells. E and RE has a .25 stun duration (This has made it's way into the tooltip as seen here https://uploads.disquscdn.com/images/e57e09b734ca66a25dc1f53b75a5842ef6e08b70eb89eb04e7763fe32aa2e52f.png ). Under certain circumstances you can hold 4 turrets. RE will occasionally have an extended stun duration.
Edit1 Additional bugs! Rylais and DH no longer proc off of Hiemerdingers turrets. DH will only proc off of the first Rocket of Heimerdinger. Should the first bring it to below 50% HP it won't matter if the others hit due to them not proccing.
Edit 2 REs final bounce procs the enhanced stun. Other bounces simply don't matter.