A noisy phone line is not going to be helpful. You sound rural, which suggests a long line with many joints. Try to get the engineer to check and remake all of the joints on the d-side on the basis that you've had multiple faults. Bad joints tend to perform OK in dry weather and cause lots of issues in wet weather.
I note you previously looking at spot SNRM figures and that is a good approach, but spot figures rarely give you the information you need. However, SNRM figures plotted really will tell you if there are significant issues with the line. Which router are you using? If it is the Plusnet Hub One, that is a BTHH5a for which there is a plug and play version of Router Stats - see the link below.
Consider setting that up, running 24x7. I recommend a sample interval of 10 seconds and 720 points per graph. You only really need the SNRM plot, unless the line is dropping a lot with very variable SYNC speed.
Superusers are not staff, but they do have a direct line of communication into the business in order to raise issues, concerns and feedback from the community.
