I once was collecting already for about a month. I applied for a bunch of jobs, interviewed and got one. I asked them to start a week later so I could collect one more full UE check.

One of the requirements of collecting was to attend a job fair after one month of collecting. I had already found a job by that point, so I didn't go. I got a letter a few weeks later that said I had to pay the last check back because I didn't attend. I challenged it and said I didn't go because I already found a job and had recently started working.

They denied my challenge. I think I still owe that money. This was over a decade ago IIRC.