The idea that you identified voltage changes when pushing on the wiring, which is likely where the problem is.
There will be a heavy gauge wire from the battery which has 12v at all times. Make sure it is tight and not corroded and the wire is not damaged in any way. (Letter B in pic 1)
If that checks good, disconnect the two connectors (letters A and C in pic 1) and inspect for pin damage where the connectors come together, inspect the wiring for any damage, or corrosion, and make certain one of the pins isn't loose in a connector.
Since there are three different connections, see if you can identify if there is one that causes the issue. That will help you narrow it down.
Also, it sounds like the alternator isn't the issue. However, it could have an internal wiring issue right off the connectors.
Please keep in mind that there is always power to the alternator. I would recommend disconnecting the negative battery terminal prior to checking connections.
Let me know what you find.
Joe
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Thursday, April 28th, 2022 AT 6:33 PM