It was originally 4 x 50w halogen GU5.3 bulbs. It's now been running 2 x 50w for the past hour and no flashing so looks to be load related. I'll try 3 x 50w and if that's still ok I'll have to swap them for 4 x 35w which will be cheaper than LEDs.
I have a 12v AC cable/track light set with 4 x 50w halogen bulbs in parallel. The transformer recently failed so I purchased a new one which is rated at 0-210W which I thought was high enough to cope with the load. The transformer I purchased is a Varilight electronic transformer YT210Z...