Styleable dropdown

I have been using the Selectize plugin to be able to add some styling to dropdowns

https://bubble.io/plugin/selectize-dropdown-1590176240624x708878169932038100

I got pretty close to what I wanted but then it breaks sometimes (not always) where the select options overlay another element on the page. There appears to be a z-index issue:

I have tried increasing z-index, makes no difference. Has anyone had similar issues? Or can recommend a different plugin?