This study claims the introgression was made from 47K to 40K years ago, more recent than thought, and not repeated. But it also claims the vast "Neanderthal DNA deserts" we see today were already present in the earliest human genomes we can find. They believe this means that evolution deleted the rest of the Neanderthal genes with dramatic speed. I like the ideas of Cambridge Professor Dr. William Amos who says there is no DNA from Neanderthal Introgression in living humans and the whole thing is an artifact o varying mutation rates.
The conclusions of the study are highly implausible and instead the evidence found completely supports the claims of Dr. Amos over and against the established narrative.