Hello,
I have just noticed that the dihedral angle obtained by Ctrl-LeftClick (in Edit mode) on Ca-C bond in protein backbone is not actually the psi dihedral (N-Ca-C-N) but rather the angle between N-Ca-C-O (shown in white on the attached picture)!
"dihedral" command shows the right value for psi (shown in yellow on the picture).
This is not a bug though it is confusing because at the sane time phi angle is calculated correctly in both cases. Furthermore the necessity of rerunning "dihedral" each time psi adjustment is needed and lack of "live-preview" is not very comfortable.
It might be worth tweaking this issue.
SDA
illustration of the text