Hi brenden,
thank you for your effort.
I tried the safe mode procedure and it seemed to work at first. After the first restart the speed was set as defined.
But after I restarted my MacBook several times the preference changed again to default with no pattern whatsoever.
Sometimes the setting stayed correct for several restarts and then it switched to default after another restart.
However it seems like this issue does not apply to changing the mouse speed on a new user account.
Does this mean I would have to create a new user account and copy all my data and settings?
By the way my current user account is defined as “Standard”, not “Admin”.
And I’m using a wireless Magic Mouse 2.
Thanks again!
Best,
Adrian