this question is a follow-up to Detecting Negative Cycles in Undirected Graphs.

When checking publications related to the problem of detecting negative cycles in weighted, undirected graphs (the apparently newest one being this one ), I saw only $b$-matching and $T$-joins being mentioned and investigated as methods for that problem.

Question:

Are there concrete examples of undirected, weighted graphs, that contain negative-cost cycles, wich the Bellman-Ford algorithm fails to detect, resp. can the existence of such graphs be proven?