Strange things happened after resizing

We decided that we will create and publish in 1920 x 1080 format. Previously we worked in 1024 x 576.  The interaction on the page works as follows.

Student must enter a value and press enter. If correct it is marked as correct when incorrect some feedback is given. Then this must be repeated two moreimes on this screen.(Basically a sentence where three values must be entered) A variable is increased by 1. If incorrect it is only increased by 0.5.  This is done to display the NEXT and PREVIOUS buttons only after all is correct or after at least two attempts per answer field to force the student to attempt to answer the question, but still offer a way out.

Now this all words fine student enters a value and press enter and feedback appears.  Student clicks in next field and enters a value and feedback appears.  Student can retry by deleting the wrong answer and enter a correct answer and upon ENTER the feedback appears.

After the resize the student MUST now click the mouse before feedback appears. It is as if the ENTER command is not being registered like before.  

The stranger fact is that on the next screen with similar interaction it still works fine.

This is weird. What am I missing