LUA dissector - combine data from 2 UDP packets, display issue

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Hello,

Following my previous question on the issue, every time I select a packet that is based on combining data from previous packet and current packet, I'm getting an error on the packet details on the custom protocol section.

Only when I select previous packet and then the current packet, I can see the dissection as I expect and without any error

How to solve the issue?

(Unfortunately, I can't provide the screenshots as it is in my private network).