Checkboxes don’t load on profiles

I have two fields which are a set of checkboxes on my profile form. On initial page load, the checkboxes are always unchecked, even if the user has some of them checked already (I can see them in the database in the usermeta table). If I reload the page, the checkboxes are now checked to match what’s listed in the database. I can reproduce in both Firefox on Mac and Chrome on Windows with the Twenty Nineteen theme and all plugins other than UM disabled. Both fields are required, which means if they load the form and make no changes and submit, it yells at them for not having anything checked.

One of the fields has 4 choices, the other has 5. I have a single-checkbox field later in the form which loads fine, and a 3-item checkbox set earlier that seems to load fine. The only difference I can see is that some of the options in the broken sets have “/” in the text. Would that break it? Why does it work after reloading then?

Ultimate Member plugin version 2.0.54

I’d post screenshots but I don’t see a way to attach images on the new topic screen.