Yes it's a timing problem, and there's no way to determine the exact one between all transformer brand and model. Adding a calibration process is possible but... usefull?

grabbing the signal directly from the li ne is the only way i see to make it work with all transformer.

Transformerless PSU is another way.... i hate that but if everything is properly done and insulated, the user shouldn't be hurt one day.

Give me a couple of days.. i'm on a rush now.