As in title. I experienced this with Garbage Worms stealing a back spear while I was holding a pearl (main hand) and a vulture mask (off hand). Every single time, the pearl would be dropped. This occurred while moving and stationary, and while swimming and not, if that helps track the bug down. I can get logs if necessary, but this doesn't strike me as the type of bug to need logs. I am playing on linux via Proton
#Hunter drops main-hand item when Garbage Worm steals back-spear
earnest fossil
hallow tusk
+1. Also Linux player, but I believe this issue applies to all platforms