flatRows contains duplicate sub-rows when pagination is enabled

[fragjulian]

TanStack Table version

8.20.6

Framework/Library version

React ^18.3.3

Describe the bug and the steps to reproduce it

When using pagination and sub-rows, the pagination row model contains sub-rows multiple times (only in flatRows).
Expected behavior: Each unique sub-row only appears exactly once in flatRows.

Your Minimal, Reproducible Example - (Sandbox Highly Recommended)

https://stackblitz.com/edit/tanstack-table-fsgapb5f?file=src%2Fmain.tsx

Screenshots or Videos (Optional)

Do you intend to try to help solve this bug with your own PR?

No, because I do not have time to dig into it

Terms & Code of Conduct

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• I understand that if my bug cannot be reliable reproduced in a debuggable environment, it will probably not be fixed and this issue may even be closed.