It’s normal for there to be a good amount of ripple on the display voltage (Vbb) in my experience. I don’t think yours is necessarily out of spec. 0.275 V out of 50 V is less than a 1% ripple so should be fine.
The display offset should be a 9 VAC sine wave with a +8 to +11 V DC offset. So with the scope on DC make sure the middle of the sine wave is between 8 to 11 V. Or use a multimeter set to DC.
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