Is the breaker a GFCI? That might cause the problem. I've heard they can be touchy with EV chargers.
It could also be a temperature issue. I would check the temp around your breaker. The I-Pace will max out a 24A charger, and 24A is the max continuous rating of a 30A breaker at usually 40C (104F) ambient. If it's hotter than that around the breaker, then it can trip once it runs 24A for a while. The I-Pace can heat up a garage while charging also. If the Smart EV pulls less amps and/or doesn't heat up the garage as much it could explain why it doesn't have a problem.
The chart below was stolen from Schneider's website for their Square D QO breakers as an example. The curves are the max rating not the continuous rating which is 80% of max.
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