When you say that the Samsung tab is in “sleep mode” is it in sleep mode with DMD2 running (either in the background or foreground)?
DMD2 is set as default launcher. It is on screen, push to side key and Tablet enter to sleep mode. At least display shut down. I do not know what else Samsung does. When I push side key again Samsung wakes up and DMD2 launcher works expect DMD2 BT connection with ODB lx.
User manual: Power key (or Side key) – The power/side key powers the Tab Active on and off. In addition, the user can tap the button to enter Awake/Sleep mode.
More info after tablet wake up:
The voltage value (e.g. 11.9V) is immediately displayed and the BT indicator is red (in failing case). When the connection is successful, the first voltage value is initially zero, and the reading becomes correct when the BT indicator turns blue.