MR6150 - Nighthawk M6 - MCC/MNC issue

I'm using the nighthawk for a while with a Belgium sim card ( Digi Belgium ) . Custom apn added. 

When I was abroad ( Holland ) last week it didn't work. But ok roaming was not enabled so enabled it , fine.

When I came back to Belgium, no luck. On the display 'searching' ... Even after rebooting.. no luck

Did a reset started over, no luck

When I put the sim card in a mobile phone all is ok .

When I put another sim in the router , that's also fine

Then I looked at the diagnostics, and I'm surprised. The MNC is not correct for my simcard. It's also detected as another provider ( BASE ) .. Contacted support and they told me to check on a mobile phone and try changing MNC. When I put the sim in a phone, the MCC/MNC was correct.... so no need to change.... When I put it back in the router, wrong MNC. ANd there is NO Way to change it on the M6 ..

Now I'm complete stuck. Support of mobile provider, tells me there is nothing wrong with their sim

Any idea? how can I tackle this on the M6 ? 

Thanks