+1, once the newer derailleur chains got down to flush pins . to pack in 9 & 10th cog.
you only shorten them once to install and add the quick link to close the loop..
rivet operation in chain making machine spreads the pin head,
pushing it out spreads the hole in the link, so it stays loose and insecure after that .
should you try pressing it back in ..
temporary at best .. time to try again with a new chain..