Weird scrolling behaviour with GUI.BeginScrollView since Unity 5.5.3

I have a game released on Steam which also runs on Linux.
The game is already almost 3 years old and still uses the old GUI and scrollviews with GUI.BeginScrollView.
It worked fine until I updated to Unity 5.5.3, when it started to behave weird. This became even worse when I updated to Unity 5.6 a few days ago.
Now players are complaining the scrolling only works very sparadicly and when it works, it works in reverse.

The issue also appears to be only on Linux and it works fine on other plattforms.

Does anyone else have the same issue and if yes know a workaround what I can do to improve the scrolling behaviour?

 

Can you file a bug report with your project? (Or a smaller project which demonstrates the same issue)

 

Environment:
Ubuntu x86_64 Bionic Beaver 18.04.1 LTS
Unity Editor 2018.2.5f1

The project attached here uses two scroll views (one of them is adapted to support touchscreen drag-scrolling).

Phase A (Unity Editor Player):
Load the project.
Preview the project using builtin Player.
1) Point the cursor over the top view.
2) Slide fingers up (wheel down). Should scroll top view down, scrollbar goes down, ok.
3) Slide fingers down (wheel up). Should scroll top view up, scrollbar goes up, ok.
4) Point the cursor over the bottom view.
5) Slide fingers up (wheel down). Should scroll bottom view down, scrollbar goes down, ok.
6) Slide fingers down (wheel up). Should scroll bottom view up, scrollbar goes up, ok.

Phase B (Standalone Binary Build):
Load the project.
Build the project and launch the binary.
1) Point the cursor over the top view.
2) Slide fingers up (wheel down). Should scroll top view down, bottom scrollbar goes up, not ok (wrong view, wrong direction).
3) Slide fingers down (wheel up). Should scroll top view up, bottom scrollbar goes down, not ok (wrong view, wrong direction).
4) Point the cursor over the bottom view.
5) Slide fingers up (wheel down). Should scroll bottom view down, top scrollbar goes up, not ok (wrong view, wrong direction).
6) Slide fingers down (wheel up). Should scroll bottom view up, top scrollbar goes down, not ok (wrong view, wrong direction).

All my guess is that from some point Y value is getting inverted for scrolling events area in the binaries built only.

There's a video file ScrollTest.ogv in the archive that demonstrates Phase B app behavior.

Hope all this helps resolving this issue. Thank you in advance!