Refurbished Garmin Montana 700I keeps shutting down-crash for no specific reason.

My first Garmin Montanan 700 I has died while charging and was replaced by a refurbished one. This new device has another problem:  it shuts down randomly.  This is very difficult to narrow down because it happens some times 5 times in ten minutes and then it can sit on my desk for 2 days in expedition mode with no crash.... I have a feeling that the Inreach usage is the cause.

Also twice I had to first remove and re insert the battery before the power button would be reactive.

I just came back from an expedition and this bug (software or hardware) makes the device un usable in expedition situations: if it shuts down you loos in reach capacity and tracking....

 Does anyone has a solve or a trouble shooting method ?

Thx