DFRobot Gravity Offline Voice Recognition stops sending I2C Codes after a while

hi

i'm using the DFRobot Gravity Offline Speech Recognition module. Everything works fine. But after a while the module recognizes the command (the voice over the speaker ist telling the command but the I2C Bus doesn't send nothing. If i power off power on the system it works like before but stops after a while (like 7 minutes and 50 recognized commands). But it could be also shorter time and below 50 commands.

Does anyone know this strange error?

The module is on 5V so it seems not to be low volted.

Any ideas?

sincerly 

hape