If I thought the lock of a knife might fail and cut my fingers, I wouldn't buy that knife.
If I thought that the lock of a knife might fail while using that knife hard, I would use a fixed-blade.
I've been using frame locks and liner locks for the past 15 years, and I've never had one become unlocked by accident.
Considering how many liner lock and frame lock knives have been in use for the past several decades, if they were experiencing a heavy rate of failure I think we would be hearing about such incidents quite often on this forum. But we don't.
When people say that liner/frame locks are unsafe, I can't help but wonder if they have actually experienced a lock failure, or if they are just repeating something they read on the internet. And if they did experience a lock failure, I can't help but wonder what they were doing with the knife.
Of course, I don't actually expect people to admit that their lock failed while using their knife in an unsafe and irresponsible manner. Instead of blaming themselves, I would expect them to blame the knife.
If you buy a quality knife, and use it as it was intended, the lock shouldn't fail.