Select: regularly failing test

[ilhan007]

Describe the bug

Hello @SAP/ui5-webcomponents-topic-p
There is a test cases failing regularly on the Travis, on the central build, and slows down the development process.
The failing test cases are:

Further log about the failure:

Please investigate what might not be robust enough, what would make it fail. It is ok if you decide to remove some parts and make it simpler. I am setting its priority to High, because it has significant impact on the review/merge process.

[nnaydenow]

Internal reference: 5112