Weird overcharging issue

If there is a voltage drop from battery to blue wire at regulator IGN, voltage will be high at battery. That usually happens with poor bulkhead connection. However since you are reading ammeter, not battery voltage, and IGN voltage, nobody will know for sure. The other possibility is poor ground at regulator mount. A poor connection at green wire will result in under voltage, not over voltage. The early regulator momentarily switches the green wire to energize the alternator field. If the regulator contacts are stuck, or green wire is shorted to 12V, then full field and over voltage will result.