Could be the starter's mounting angle. Some cars have shims for this issue. Or maybe an internal manufacturing defect.
It could be the solenoid, or the wiring. Or the ignition switch itself. Possibly the relay.
One thing that can cause intermittent electrical problems, is the grounding. There should be a braided ground strap, or wire, in addition to the main negative terminal cable. Most vehicles have them for a reason.
All this speculation is the reason I mention the amp draw first. That's a real number, and not subject to change with each start. So it isn't affected by anything else. It quickly rules out, or points to the starter as the culprit. Because the engine takes the same effort to turn over, each, and every time.
Unless you're ready to start replacing parts, hoping to get lucky. You'll have to test each component individually.
Also I'd load test the battery. Voltage testing isn't enough. I test my batteries three different ways. Hydrometer, voltage, and the load test, which is the best for knowing battery condition. These tests all tell something slightly different, while confirming what the other tests show. A new battery isn't really proof of anything. It's unlikely, but they can go bad early on.