Hi, please check the video:
Red side just have a Image to block the drag event, and green side have a script to handle drag event.
As you can see, drag on green side only is good, but touch red side at the same time, the drag event data will be changed as well.
unitypackage file attached for anybody test
Thanks a lot!
7878043–1005595–TouchTest.unitypackage (14.4 KB)
Ooo, this looks like it may be a hardware thing! 
My favorite kind of quirk.
What device?
Hi Fenrisul, I tested it on HTC U11 and Samsung A52, both have the same problem.
I quite sure the problem is not about device, below is unitypackage and apk file, anybody please help to test. thanks a lot!
apk file:
https://drive.google.com/file/d/19GNWyd3ndnxPmgziC7qgKMu512f-X3aj/view?usp=sharing
7878043–1005595–TouchTest.unitypackage (14.4 KB)