First step would be to check if the Bluetooth setup is correct. You can read the article on Bluetooth connection issues here - I'm having trouble with my Bluetooth connection and frequent data loss.
Data loss only during cap mounting
During cap mounting it's possible that the Bluetooth signal is weakened due to a lot of people around the participant (if there's multiple people setting up). This is not very common, but could happen.
In this case, make sure to use the lowest sampling frequency - 250Hz during mounting of the cap. Later, you can set the sampling rate to a higher value for recording.
Always make sure to have the most updated software for your experiment. You can download it from our website.