Old TV signal hit village broadband for 18 months

Was this just causing issues with wifi or did it affect the actual DSL signals?

DSL ought to be resistant to most kinds of noise. In most cases, single frequency noise results in a tiny reduction in bandwidth as that single frequency bin can't be used.

It looks like in this case, a design deficiency in DSL contributed to the issue. Specifically, DSL assumes the amount of SNR at each frequency stays constant. A better design would adjust the number of bits and the power in each frequency bin to handle noise sources changing without requiring a full disconnect and resync which takes a few minutes and leaves the customer without service.