The Bluetooth connection can become unstable, meaning that the connection has delays without data loss. This can cause high drifts. However, if you set the parameters “Drift Tolerance (ms)” to 100, and “Jitter Estimation Count for Drift” to 1000 (their maximum values), the drift tolerance is increased, and you should not be facing this problem. It is important to note that the drifts will not influence the recorded signal, while they may have influence on the real-time data processing. Another thing that you can try is to use the LSL import (instead of mBrainTrain Smarting), and then stream the data from the SMARTING Streamer to OpenViBE (via LSL). This may also decrease the drift of the signal.