Version of BuzzTV 5 ? from liveTV, press menu, and should be on bottom of the menu (5.0.xxx)
MAC or XC type login ?
If it is XC, have you tried changing the "stream type" ? If it is set to Automatic, try setting it to M3U/HLS or TS.
Also, for recordings, SD card is not the optimal option. USB 3 drive is the best option. Even if you SD card is a super fast card, there is no specs on what controller/speed is on the SD slot on the buzz boxes. SD card on buzz boxes is typically used for recovery/firmware updates. I know many who have used SD cards, and eventually switched to a USB3 drive and problems went away (just a thought).
Now, for the fact that 2 recording worked even though you have a single stream sub, that depends on your provider and how they enforce it. If you are in LiveTV, and go to menu->Settings->Account info, does it show active and max connections ?
Keep in mind that if there is a glitch in the stream, or if the stream gets redirected by the providers, the recording will stop (and not resume). The stream needs to be continuous and flawless.