I have the same problem in PS 1.7.6.9 for few days, no changes have been made on Prestashop but it is constantly sending mails with log information. First I got (127) Unauthorized messages and then (127) Internal Server Error.
This happens when I am on the PS dashboard, I tried to deactivate the PS_Metrics module which was activated on this page and it seems that PS does not produce any more errors ...
They have certainly changed something in the way PS_Metrics works through their API ...
(I had tried to deactivate the mails but this option in the back office to deactivate the log mails does not seem to work for this type of errors.)