Yes, a little bit further in my trip this morning I got the "HSPA+, no internet" again as well. Sometimes it does work to disconnect, wait a while and reconnec, but in most cases it starts asking for an APN. In which case you are screwed.
This morning I was almost at the office, so I thought to let it be for a while. And same as you: I also had issues with WiFi while in the office. I needed to restart the tablet not only to get LTE to work again, but also to let WiFi work again.
But, mark my words: we will not get a (helpful) response on this one! If resetting the device, dsim /online, wsreset, reinstall the drivers etc doesn't work Microsoft support seems to be lost.
In the Netherlands you can't really get support on the LTE part as the tablet officially was never sold in the Netherlands, but I am pretty sure people in other countries experience the same issues.
Let's see what happens...I guess...nothing. I mean: the official answer is to contact the provider. The provider has worked with me high and low! This really is not their issue! As shown before: my cell phone sitting next to the tablet on the same network
does get internet on LTE. And if it switches to HSPA+ occasionally (I have to admit that) it doesn't get internet either...but: it will switch back to LTE, UMTS or whatever without the need to restart! That's all I'm asking for.
I do understand this is not something that is fixed over night, but it has been 4 months since I last heard people working on this.