When using UnionAsync function, CSG returned error code -11

my script was planning to use UnionAsync a few times but failed on the third use
the first three Union i tried to make:
1 - part:UnionAsync({10 parts})
2 - part2:UnionAsync({10 parts2})
3 - part3:UnionAsync({129 parts3 })
on the third it gave the error message:

-Something went wrong. CSG returned error code -11. Please file a bug report, preferably with a file containing the problematic object(s).

the line with the error was where the UnionAsync function was.
Error Line:

local newUnion = Children[1]:UnionAsync(otherParts)

and:

local a:Part = workspace.model.test local b = a.Parent:GetChildren() table.remove(b,1) local newUnion = a.Parent:GetChildren()[1]:UnionAsync(b) newUnion.Parent = workspace

when i tried this code i got error again,
but when I click on studio’s own Union button, I didn’t get such an error
all part’s ClassName is “Part”

File:
UnionAsync Test.rbxl (35.4 KB)

same thing happens to me like i’m trying to union the unioned parts

trying to separate the unions several times and it worked again

Late reply, but UnionAsync() only works on BaseParts or Parts. You can’t use UnionAsync() ON AN UNION.