Receiving it right now near Boston on my NetSDR with longwire. It is fading heavily and never gets very strong. The only other station on 870 is WHCU, also fading badly. To me, the wobbler sounds like there is some sort of phasing effect, either in the modulation or between 2 RF signals, but that may just be a propagation effect.
There are posts about it on other forums going back at least as far as 2013, on 870 and 650. It doesn't seem that the same bad transmitter(s) would still be in use, unless it a common issue with a particular model. Possibly it is an old jamming source that occasionally gets switched into the audio chain, perhaps accidentally.