Erratic flicking/disappearing of checkboxes

Forgive my ignorance – I’m very new to ASOC. Couldn’t seem to find anything relating to this problem.

I’m in the process of making an app, and the UI objects are… acting funny. Primarily my two checkboxes. When toggling one of them on and off, it flickers sometimes, and once in a while it disappears entirely. Toggling it again or otherwise forcing the app to redraw (e.g. switching to another program and then back) makes it again show up normally. Here’s a screenshot of a checkbox’s label mysteriously going missing:

Sometimes the checkboxes go missing instead of / in addition to the labels.

Any ideas?