That's a strong signal that your team isn't doing well. Significant problems should have been spotted at a software design stage, or raised in standups, or identified in a pairing session. The earlier you can find an issue the simpler it is to fix, so waiting until the last moment (e.g. PR) means you're spending far more time fixing issues than necessary.
As for finding bugs, what happens if you miss them? Do they go out to production and potentially lose user data? Finding bugs in PR is a big problem. For a start it shows your automated tests aren't good enough, and secondly it shows the devs aren't checking their code works well enough.
If you do them at all, PRs should be a gate for checking whether the code meets the team's quality bar, not if it even works. The team should be able to deliver working code without them.
As for finding bugs, what happens if you miss them? Do they go out to production and potentially lose user data? Finding bugs in PR is a big problem. For a start it shows your automated tests aren't good enough, and secondly it shows the devs aren't checking their code works well enough.
If you do them at all, PRs should be a gate for checking whether the code meets the team's quality bar, not if it even works. The team should be able to deliver working code without them.