The biggest polling "miss" is 6% and that was one state 16 years ago, but they even included one that was <1%
Standard margin of error is around 3.5% with a 95% confidence, and the vast majority of "misses" were well within that. Depending on survey tho, margins if 5% or even higher do happen. But even if it was 2.5% over the margin of error, polls aren't perfect representation and sometimes it does happen.
The big problem is what they spend the first part of the article on: national polling
It's completely useless, it shouldn't be because we should be using a national popular vote. Until we fix that a national poll means nothing.
I just hate people got obsessed with the whole "polls aren't real, they're dirty liars!" When polls showed Biden wasn't going to be able to get it done.