I’d like to share the answer to this.
The problem is that set member in struct requires that a reference of a struct is feed in. So just passing a copy of that struct won’t do the job.
There is a get node for arrays called “get by ref” which returns a reference (shown as shape instead of the circle on the get node). Or more elegantly put here is how it should look:
Note that you cannot use the foreachloop node since it returns copy of any array you feed into it.