Charging from dock through TB3 tests

I have a XPS 13 9300 connected by TB3 to a VisionTek VT4800 dock. The dock has a power adapter and specs say it can make up to 60 watt charge to a laptop. Monitor DP1.4, ethernet and 2 USB devices are connected to the dock and work fine. BIOS is unaltered. Drivers and BIOS are up-to-date.

Here's my tests with just the TB3 connected to the XPS, XPS power adapter not connected.

After a full shutdown and reboot the dock charges the XPS.

If the dock is charging and the XPS is restarted, put to sleep, or lid closed; it remains charging after becoming active again.

If the dock is not charging doing any of the above does not start the charging.

If the XPS is running and I put it on my desk and connect the TB3 no charging starts.

In other words the only way to start the dock charging is a shutdown and reboot. If it's charging it remains charging after coming alive again.

I'm often in the situation where I'm working with the XPS unconnected away from my desk. When I come to the desk (XPS may be open, sleeping or just lid closed), connect the dock, I'd like the charging to fire up. Having to shutdown and reboot is too much.

These forums show there's problems with dock charging and TB3 with the 9300. Do other versions of the XPS function as above, or is there a 9300 problem with my setup? Is it standard for nothing to happen when the TB3 is connected or unconnected? Or is it just with the 9300?

Thanks