For some reason my build definition are not working properly if long path mappings. If I were using the path $/Project/Samples it works OK.
My build has this in the repository tab:
Then the logs show that there is no SLN found, and I confirmed that nothing was downloaded to the agent working folders:
For me it's a bug when getting sources, as I can't see a good why it is not getting correctly the files. I already tried to add files in some folders above and it works. Some ideas?