We’re not really sure. There is no generally understood mechanism by which the field control, old or now, would be able to spontaneously cause a disconnect during a match.
However, throughout my 9 years in this competition I have seen too many simultaneous alliance disconnects or even whole field simultaneous disconnects to believe that there is no way for the field to cause one.
You can check out this thread for a great explanation of the older field control hardware by @jpearman himself, as well as a discussion about potential field faults in the 2017-2018 season:
As a ref my rule of thumb is that if no other teams were simultaneously affected, then it was probably an isolated incident to that robot from bad radio mounting, damaged wires, or plain bad luck. Am I 100% sure that the field wasn’t involved? No, but since I have no way to actually verify either way, I have to choose the most likely outcome. If multiple teams on the same field were affected simultaneously and it arguably changed the outcome of the match however, then that’s worth looking into a replay for.