I suggest slowing down the rate at which you are polling the device. You may be asking for data more frequently than the gateway can handle. At first it may buffer the pending requests, but it could be locking up when the buffer gets full. Cycling power flushes the buffer. By slowing your polling to a rate such that the gateway has responded to each data request before the next request is received, you eliminate the usage of the buffer.
Please note that I have never used the device you are having problems with. I am just offering a possible explanation for the behavior you're experiencing and a potential remedy. Also, you didn't mention what protocol you're using for communications and whether it is a communications driver you purchased or one you programmed yourself.