Error after sending email from email digest

Hello all,

I receive emails normally from ERPNext (through Sendgrid integration). However if I go to email digest and I choose “Send Now” the following happens:
1- I receive the small pop-up at the bottom right of the screen that says that the email is sent (and I do receive it, no problems there).
2- a few seconds later I receive an error message the says “User None not found”.
3- The error keeps coming every few seconds, and stops me from using ERPNext properly.
4- If I am logged out, I won’t be able to log in again since this same error keeps coming every time I go to the login page.
5- This situation will continue like this for almost a full day then it’s rectified by itself without doing anything!

Do you have any guidance on how to fix it?

Best regards,

I am also getting the same issue. Kindly give a solution to fix it.