What do I look for when buying a used gas cooktop
I would be more worried about the igniter or if electronic how often it fails.
I have been asked several times if I could repair them and the high voltage circuits are usually potted and not repairable.
With potted electronics you are stuck purchasing expensive replacement parts.
And that may be the reason to sell (or a remodel).
I am not aware of any real safety concerns and any alerts could be online using the brand and model.