Possibly you have exceeded the limits of the layout, taking up more space (in the horizontal direction).
When considering mobile devices, please change the display mode of the questions to "dynamic", see Questionnaires for Smartphones.
Often it's also useful to give the layout more space (width), see Survey Layouts
And it's also often a good idea to check if width definitions in the questions use sensible values.
If that does not solve your issue, feel free to post a pretest URL leading directly (!) to the questionnaire page that causes the issues.