Wiring issues: If your wiring is damaged, perhaps it's corroded, burned through, loose, or anything to that effect, it could affect the turn signal circuit's performance. Bad relay or flasher ...

Once known as a turn signal or blinker switch, this lever now also controls headlights, high beams, emergency flashers, ...

Flasher circuits were in regular use well into the 1990s. The original Mazda Miata has a very similar circuit tucked up under the dashboard to run the turn signals. These circuits can be hard to ...