Honestly I really don’t know what’s causing it. We’ve tried everything we can, including changing the Ethernet library and released 2.1.9(10) which you’ve tried. We have never been able to reproduce the issue internally, so without observing the issue happening we can’t debug it. Also, what zsolesz79 was asking is a separate issue — it has to do with a corrupted flash memory string, this has nothing to do with losing Ethernet connection.