nonsense, it's free and can be done easily by yourself. Agents are good for all your visa issues but this one isn't a visa, just a straight forward digital arrival card.
Same here, one of my accounts is 13 years old and the Bangkok bank one is 20+ years old. No issues, no messages regarding this, nothing blocked and all good.
I did one in Pattaya, September last year. I was in at 8.30 am and out by 9.05 am. It's not bad if you can get the form and fill it out prior to getting there. Just get the all they ask for and it's only 1900 baht doing it yourself.