Hi Charlie1992,
Thank you for sharing those extra details. I’ll add them to my report for the team. Looking at cloth and leather first may help the team to narrow this down if they’re more likely to vanish.
Forum user Jbro shared this video in their report where they described similar issues to yours the other day… Is this how it appears for you too? Stranded Deep CO-OP Bug - YouTube
(Jbro’s original post: [PS5][2083][COOP]Items disappearing from chests)
Have you ever been able to interact with the items when they appear outside the chests or are they just there in a visual sense?