Try using your phone as a wifi hotspot, connect both devices to that and batch import. If it goes through without a problem, then you know that the router is the problem.
I mentioned earlier - I batch imported 3700 PDFs without an issue. I've batch imported well over 5000 files before without a problem, so I'm not sure what you mean by reaching a limit of what it can handle with 900 files. I'm using TCP which should be fault tolerant, so something must be interrupting the connection completely for those failures to happen unless the problem is happening for you with the same PDF every time. If that is happening, then it could point to an entirely different problem.
Mike
I mentioned earlier - I batch imported 3700 PDFs without an issue. I've batch imported well over 5000 files before without a problem, so I'm not sure what you mean by reaching a limit of what it can handle with 900 files. I'm using TCP which should be fault tolerant, so something must be interrupting the connection completely for those failures to happen unless the problem is happening for you with the same PDF every time. If that is happening, then it could point to an entirely different problem.
Mike