DG-1 will be very tricky to capture accurately, as you will have multiple dofs at the same physical position, which the algorithm cannot logical distinguish.
If you want something discontinuous transfered, i would either:
- use a projection, as described here:
L2 projection of fine mesh solution to a coarse mesh - #6 by dokken - use DG-0, whose coordinate is at the cell center, and does not have duplicates.