I don't know what is wrong, but can you try using wired ethernet? If this works fine, it means the wireless is the problem. If wired has the same problem, then it might be a problem with the formatting of the drive.
My SSD recently had problems after almost 5 years of use. Music paused, and copies failed. I swapped the drive out with a Samsung 860 EVO, and the system works better than ever. However, your problem sounds like more of a severe problem.