TP-Link MR200 LTE router - Modem resets after restart

I've installed LEDE on a TP-Link MR200 LTE Router following
Everything works perfectly fine, expect one thing. After a restart the modem (not router) settings - accessible through are reset.

I would appreciate any advice on how to make my modem/provider settings (especially the apn) permanent.

Thank you!

OK, so the router keeps its settings, just the modem configuration?

How are you configuring the modem? Which packages did you install to support it?

Thanks, jeff. Yes, correct. The router is fine, only the modem is losing its settings.
I'm configuring the modem via the web interface at I would prefer to do this via a config file or script but could not find one.
I've only installed the default packages that come with LEDE, no additional ones. may be helpful, if you haven't already seen it.