Any chance you can share the page you’re working in or can recreate a basic version of what you’re trying to do in a shareable document? I’m a super new Coda user but that’s always the first question/bit of feedback I get when I post questions to this forum…
Can you confirm that the column type where your formula is living is Select List?
I’m not sure that this will do what you’re looking for, but I found some info in another forum post about ListCombine and it recommended adding this additional filter to the end of my formula. It eliminated my issues with blanks and those brackets that were being displayed. Might be a place to start?