Pavlovia initialising experiment not in the centre

I have had the following problem when I am running a Pavlovia experiment on phone.

In the initialising the experiment page, the text “initializing the experiment” is not in the centre of the screen. As a result, the initialising page (page where we put participant number, etc.) is not in the centre.Then the whole interface of the experiment is shifted downwards and some stimulus in the bottom of the screen cannot be seen.

This problem can be solved by refreshing as the screen will align back to normal again. This problem is also not reproducible where it randomly appears. Does anyone know why this will happen? Thank you for your help