Modulation drops in response to unfavourable line conditions, usually a degree of noise. As there's plenty of headroom on the D3.1 channel, dropping modulation may not make any difference to the speed or performance of the connection, and VM won't assign a technician unless there's a demonstrable performance fault.
I'm a Very Insightful Person, I'm here to share knowledge, I don't work for Virgin Media. Learn more
Have I helped? Click Mark as Helpful Answer or use Kudos to say thanks