LED conversion, 1971 Scamp

Hi to all. I am in the process of converting all bulbs to LED, but have encountered a problem which does not make any sense.
Headlights, No problem
Back-up Lights, No problem
Signal Lights, PROBLEM. Started by installing an Electronic Flasher, Grote 44810. Then installed 2 rear (1157) LED red bulbs, all OK, then Installed 2 front (1157) LED amber bulbs. Now all 4 flash whichever direction I switch to.
I switched bulbs from socket to socket with same results.
Then I replaced the 2 front LED's with the old incandescent and everything works the way it should. There is NO reason for this issue that I can see. I also have a 1956 Dodge Custom Royal and have replaced every bulb in the car with LED's without this problem. I have used the same manufacture's bulbs in the Scamp.
What's going on?

Del S

Hi Del. What LED H/L's did you get?