I have noticed that in my area the DC on the line situations come and go, when they occur they persist for a few weeks. Whenever there's a holiday, that's when it starts and persists.... the cause is most likely overloading of the entire neighborhood, and it got much, much worse since the outbreak of the pandemic with most people staying at home / working from home / losing jobs & full time at home watching TV and hanging on all times to their electronic devices.
The most practical solution I found is to bleed the DC when it happens with a parallel inductor (Richard Grey - RGPC makes such device, for example). Then I get a major improvement in sound quality in all areas.
However, when there's no DC on the line, I keep the RGPC off.
This way I can avoid the negatives of a series DC blocker...