OP: Does your tablet have a power socket separate from the usb port? If not, and if the usb gps device is not powered, then you might have a problem using usb.
I use an sd card reader occasionally with my Nexus 7. It's extremely flakey - sometimes works, sometimes doesn't. I've had photo cards corrupted too. On forums like xda developers people often report the same. Some blame cheap otg cables, but I bought one recommended there. I've found that it works better when the tablet is fully charged. I think my card reader requires more power/voltage than the the tablet can reliably provide. This is only a guess BTW, but since then I've only used it when fully charged and had fewer (not no) problems. The card reader was very cheap, and may be off-spec.
So you might need to keep the tablet plugged in. It might be possible to run it through a powered usb hub - don't know if that works with otg. I can envisage a 'powered otg cable' too - maybe that exists.
