Your downstream SNR is too low on channels 13 and 14, and may be causing the issue. VM will need to take a closer look at your connection.
You will need to contact VM for resolution, either by waiting here about a week until a VM Forum Team Member picks up the thread, or give them a call on 150 from a VM line or 0345 454 1111 for a quicker response.
Thanks for taking the time to post on the community.
Sorry to read you are experiencing an issue with your broadband connection.
As griffin mentioned, the Modem SNR (signal to noise ratio) for downstream on 2 channels are too low. For this I can arrange an engineer appointment and I have sent you a PM (purple envelope icon, right corner) with some details for you to confirm please.
Otherwise the network is running stable, which is good. In the meantime, were the speed tests completed through a wired or wireless connection?