[svnt]

I didn’t go look up the quote but based on your version here it sounds like roughly half (44%) had some kind of suboptimality, and of those roughly a quarter (26%) had serious problems preventing them from being relied on.

That means 11% of the total papers should be discarded, which means 89% of the papers can be used.

[InSteady]

As per usual, science reporting fails to use precise language. It can be interpreted either way, although I think your interpretation is the slightly larger leap based on phrasing. In any case, it is far below the 70% (and not directed broadly at all scientific research) that GP states.

[svnt]

I went and read the article but have not tracked down the original paper.

It is at least 26%, because that was the percentage of studies that provided access to their data that proved faked or fatally flawed.

It may be substantially higher.