The core. It's probably loose because it's an aftermarket one. It's likely no less safe than the original

Any chance it fails somehow and locks me out?

Did the locksmith give you any kind of guarantee? They should stand behind their workmanship.

>locksmith had to come and drill the lock out.

WTH? Any locksmith worth his salt should have been able to pick any standard residential lock in seconds. Why did he feel the need to drill it?

And if the new core is loose it's definitely less secure. Probably some cheap AliExpress knockoff that doesn't fit right.

At this point I'd just replace the whole handle. Recoring it is more of a pain than it's worth.

They said they couldn’t because there’s a blocker on the front door preventing anything from slipping in. Or is that BS?

A pick or bump key goes in the same hole as the key. Sounds odd to me, but ???

BS. Locks are for honest people.

Your key is a chunk of metal, what is it doing in your lock that his whole toolbox is incapable of doing?

100-200 to pick a lock 200 to drill it plus 150 to install a new one plus 100 profit on said new lock....

Your locksmith is a con man

If a standard metal key can open the lock, so can his tools of similar material and size. The locksmith scammed you, as he more than likely charged a hefty sum to replace the lock (with one of poor quality even). There is no reason why he shouldn’t be able to pick it.

What type of lock is it?