Starting ionic app starts with a grey line


#1

Since several weeks I have the following issue:
Everytime I start my app I see a grey line in the middle.
Not only in the browsers but also on the devices.

Does anyone has any idea of how to get rid of such a line?
As far as I can find I dont have anything strange in my css.

Point of remark: The line only comes up when I start the app.