I've had a mobile hotspot for 3 months and this problem is getting worse. The device consistently shows a strong signal, 4 or 5 bars, but frequently my phone or laptop will say I have no internet connection, even though the Wi-Fi connection is also strong. This lasts anywhere from a few seconds to a few minutes. Even when there is a connection it's often so unstable that email will not download.
Since the hotspot is for data only this makes it almost useless. I did a factory reset and it did not solve the problem.