Originally Posted by GrantYJ
Do you have enough resistance to trip your blinker relay? If you don't, it'll do what you're describing. If you do have enough resistance, it's most likely a ground issue.
^^This is a very common cause written about.
The variance in your symptoms is odd, but I want to add my .02 on signal experience and LEDs:
Before I added LED's, I had issue of using my turn signal, it would remain solidly lit, and turned out I just had a front bulb burned out - so check all your bulbs first.
I will add, though, that I never addressed the resistance issue and only issue is a split second delay in the turn signal activating now... guess I lucked out.