help me to fix a bug in a frequency generator (arduino)

Hello, I have a frequency generator made with a arduino UNO + AD9833 + TIP31+ step up converter (DC) I can set the frequency via the serial monitor in the arduino software Then the circuit can be unplugged from the computer and powered by a 12V power source and will work independantly The circuit produces an electric signal with a min voltage of 0V, max voltage between 12V to 48V (with 1V precision) (set with a step up converter), frequency between 1hz to 100000hz (with 1hz precision) (set with serial monitor), square waveform, 50% duty cycle, the device works well but there was a problem (bug / error) that the designer of the circuit did not manage to fix : sometimes the frequency which is uploaded to the device results in an appropriate signal, but sometimes, for some reason, this results in a weird senseless signal. (min voltage, max voltage are not stable, frequency is not stable, waveform is like noise) Your work, if you accept it, will consist in finding the cause of the problem, and proposing a solution to fix it. (i will provide the schematic of the circuit) additionaly, i want to add a mod to the circuit : ->i want to have a feedback message in the serial monitor, to be sure that the frequency that i have uploaded is correct. (or maybe display the frequency on a small external screen ?) Once the device works as described, the work will be considered finished and i will release the milestone(s) At the end, i will create another milestone to pay your freelancer fees. I am flexible for the time it takes or the money it requires to complete this project, as long as it is justified and reasonable... If you have any questions, don't hesitate to ask. Thanks for your help,