CPacketRecipePlacement can create item stacks with stack size higher than max stack size
Based on 1.12 decompiled using MCP 9.40 PRE 1
The bug
The packet CPacketRecipePlacement can create item stacks with stack sizes higher than the maximum item stack size of that item. This can be done by either using the "from open container to inventory" item movement (see also MC-119011) or the "from inventory to open container" item movement (see also MC-119013) since in both cases the used methods do not test if the new stack size would be higher than the maximum stack size.