@IreneCheeseman Keep an eye on the downstream data - the table you posted before showed uncorrectable (post-RS) errors breaking through on the downstream channel around 410 MHz - that's a frequency used by emergency services, so it seems likely to be radio frequency noise ingress through a faulty connection of some sort, or a damaged cable.
If the post-RS errors keep cropping up around that frequency, then irrespective of VM's staff saying they can't see anything, then there is something that is wrong. The only thing within your control here is to check all VM coax cable joints are properly secured and any securing nuts are done up finger tight, and if there's any VM coax extensions that they have properly fitted coax cables or unused ports have a proper end cap. If that isn't applicable, or you check what you can and the problem continues, then you need a technician to come and sort out the connection.
Sometimes these faults can be caused by customers buying unsuitable coax extensions to move their hub, as although all coax cable looks the same, it isn't always to the same technical standard. Due to the way VM's cable works, the problem could even be caused by a neighbour doing that, as it can introduce noise that affects multiple customers. But that's still VM's problem to find and fix.
