Strange "freezing" behaviour brand new XPS 13

I have a new XPS 13 (16 GB mem) i7 windows 10 64bit and since I got it (a few weeks ago) I have been having the following very annoying problem. At random times (although it seems to happen quite a bit when the screen comes on after the laptop has been on but with screen off for a while. This does also happen with the DA200 not connected which would point to video driver)  the excel GUI (all the text)disappears (i.e. when I click File upper left hand) no text is visible also the whole menu bar ir missing text and the cells freeze up (not that you could do much with the whole GUI missing). Now you could say ths is an excel issue and not Dell XPS 13 issue but the resolution of this is to either disconnect my external (VGA) monitor or reconnect the external monitor. Once this is done excel immediately goes back to normal. In cases where I am not using an external monitor disconnecting and reconnecting the DA200 hub (with at that time only network cable connected) also does the trick.

Note this behavior also happens with many excel spreadsheet open but that is the way I work and did with my 7 year old previous laptop..

So there appears to be an issue with the DA200 connector/driver, the video driver or something unrelated...

I migrated from a 7 year old Dell E4300 and NEVER had any problems like (using exact same excel 2013 64 bit by the way) this and am very disappointed that this is now happening on the new machine

See attached JPG to see what it looks like when this happens.

Any suggestions on how to fix/avoid this issue?

Eric