Bit Manipulation - Find Two Missing Numbers
The following Python function attempts to find two missing numbers using XOR partitioning but sometimes produces incorrect results. What is the likely cause?
```python
def find_missing_bug(n, arr):
xor_all = 0
for i in range(1, n+1):
xor_all ^= i
for num in arr:
xor_all ^= num
set_bit = xor_all & (-xor_all)
x = 0
y = 0
for i in range(1, n+1):
if i & set_bit:
x ^= i
else:
y ^= i
for num in arr:
if num & set_bit:
x ^= num
else:
y ^= num
return [x, y]
```