Ok SAU friends, some updates.
Searched high and low for a new relay, and found an R34 one. As expected, they have an identical exterior appearance and plug.
Swapped the relay, and same issue- all the lights work, just flash fast. Hazard light circuit flashes normal speed.
Pretty confused by this. Like I said, all the bulbs are conventional, non LED.
I am tempted to buy one of those adjustable knob relays and just artificially slow it down, if that makes sense, also will try replacing some of the lights such as the rears to see if a new bulb helps. Unsure what else to try…