Scaling pitch bend automation in the key editor is performed relative to the value of -8192 instead of 0. As a consequence, scaling changes positive values into negative, and vice versa - depending on the direction of scaling. Using Cubase 10.0.10.
By what method are you scaling?
Thanks for pointing me in the right direction. I didn’t find the “Scale Around Absolute Center” dot before. It was an user error - I apologize.
Voilà! 
