Yes, such a problem does exist. The kangaroos still find the DP, because of their huge amounts, but the paths are too short and the first DP found by single kangaroo is always much worse than the subsequent ones.

As for me, I launched JLP Kangaroo with specially modified grid size, group size and other slight improvements, lets call it "fast kangaroos". But I personally know programming in CUDA quite poorly, so I couldn't write a good kernel for these conditions, and I couldn't achieve the necessary speed increase so that, so to speak, quality worked, not quantity.