That excellent you have acquired the narrow track Sankey. Sounds like the flasher relay problem, you can get an upgraded flasher relay unit from any car or caravan accessories shop or first check to see if one of the bulbs are out on either LWt or trailer. Secondly if someone presses brake pedal when hazards are flashing with trailer connected and a light goes dimmer then suspect a bad earth problem, if the latter happens clean earth connection to restore to normal. Hope this may help. Good luck with your new trailer sounds good.
Regards Ernest