Which FW are you on and which carrier are you using, apparently your carrier settings are fine and stay the same when trying to re establish the connection on LTE? I´d say that its by design as Meraki MX:s with cellular tend to think that lte is only for backup not primary. Seen this happen a lot back in 2018 when cellular models where introduced - firmware updates fixed some of the issues out there back in early 2019.
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