Even with the new switches, it sounds like a connection issue. The starter places a heavy load on the system. If there is a weak connection, this is what often happens. If you think about it, there is only 12v no matter what with the engine off. Unless you have something wired wrong, that really shouldn't hurt the switch. You aren't blowing any fuses that would indicate a short.
Disconnect the battery and then reconnect it to see if the same thing happens.
Let me know. Also, follow the ground from the battery to the engine block and there is a body ground near the battery. See the attached pic. Check to make sure the positive and neg terminals are clean and tight on the battery.
Joe
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Friday, August 14th, 2020 AT 10:00 PM