Kenworth T370 turn signal/hazard issue

I’ve got a weird issue on our 17’ t370. For the past 2 months the turn signals/hazards will not work for the first 20-40 minutes when starting the truck. Some days they work right away but I’d say 80% of the time they don’t. There are no lights on the dash and the signals don’t flash, but they ALWAYS come back after a short while and continue to work for the rest of the day.

People I’ve talked to suggested putting in a new flasher, others say it’s probably a ground issue. What are your thoughts??
Thank you!