indicator help

[Rumbles]

Need a bit of advice i helped my friend fit his dominator headlights tonight to his 99 600 and once they were on along with his new indicators , they wouldnt work correctly .. assuming it was a fuse we checked but it was fine , when put back in the right indicators would flash fine until they were cancelled but wouldn't work again after , so we pulled the fuse again and once it was back in we tried the left indicators and they done the same , work fine until they were cancelled then not work again after ..
He's ordered new led ones anyway along with a relay so I'm hoping this sorts it .. does anyone have an idea as to why this is happening ? Cheers