The only reason I had a WFCO converter is because our TT came with one.
It would overcharge the battery to the point of killing it in a 2 year period, despite constantly adding DI water. 3 batteries in 6 years.
The intensity of the 12V lighting inside the camper would vary greatly depending on the load.
The converter had a high pitched 'whistle' at night with no load on it.
Thankfully, it DIED. I gladly replaced it with an IOTA 55A 3 stage charger. Lights never flicker or dim, no noise from the converter, and the battery is no longer overcharged.