Could it be that your button1 is located too close to select1 so when you tap the button, select1 is calling its select1_onlclick function at the same time. Try moving the button further away from select1.
Found a solution. The problem is a subtle one: It’s trying to update Select1 before the code for Button1 finishes. Safari must have introduced some sort of timing problem.
Here’s what works for me: Clicking the button calls the function to refresh Select1 a tenth of a second later. That gives the Button1_onclick() function time to complete.