This is an old bug, nothing to do with 1.5.5.
I prefer to use the "get UTC time from computer" option, because it takes the DST into consideration. However, the grayline window is one hour behind the real sunrise/sunset.
You can use the manual setting UTC 3, grayline 2 and sunrise/set 3 to get also the grayline correct, but then you have to remember to change the settings twice a year.
73 de Pekka oh2bsc