Ericsson has manufactured probably millions of faulty 3G WWAN modules that hang after few minutes to few hours of use. There's driver and firmware updates out that may sometimes help but usually only by extending time before hang bit longer.
Dell Latitude 10 Tablet, identified as ST2 Late-2012 by Dell, really sucks. It's shipped with very first Win 8.0 build and after two years of updates it's barely usable with Win 8.1 + all available updates and fixes. I wanted to give Windows 10 try on it as already being worst tablet ever it can hardly get any worse, right? Reinstalling Win 8.1 goes exactly like Win 10 so below applies to both.
After realizing that LSI SAS1078 based controller wouldn't do what I want I ended up purchasing card from eBay, 65€ including shipping for unused, new in box Dell PERC H310. Prices are bit higher than I like, but this was acceptable knowing it will do exactly what I need. Despite trying hard card will still show up as DELL after making these changes but it's in IT-mode and accepts generic LSI firmware.