i noticed this bug the other day while playing on my server, in this bug it allows you to pick up more items than is capable of your invintory space but when you pick them up they disipear.
MC-40974
items vanish when picked up with full invintory!
Resolved
Cannot Reproduce
0
Please attach the complete output of the "Development console" tab of the launcher.
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If the launcher closes after game start, please edit your profile and select "Launcher visibility" then, "Keep the launcher open".