I guess I wasn't clear. The thread I linked to says a combination relay that appears good can act up intermittently due to poor solder joints. I'd have less trust for a relay pulled out of another car because the act of pulling it out could stress the solder joints even further. You could try wiggling the combination relay while operating the turn signals to see if they operate intermittently. that would confirm a bad connection in the relay. And I assume your fuses are all clean.

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1974 Porsche 914 | 1980 Porsche 911SC
2002 Porsche 911 | 2002 Mitsubishi Montero | 2011 VW Golf