SD25TB4 HDMI Output does not output 4k60hz

- I have a Dell Latitude 5440 Laptop with Intel Iris Graphics, with TB4
- I have a single LG UC88 34 inch Ultrawide monitor that supports HDMI 2.0, and has a max resolution of 3440 x 1440 60hz
- When the monitor is connected the SD25TB4 dock via HDMI, the max resolution is 3440 x 1440 @ 49.99hz
- When the monitor is connected direct to the HDMI port on the laptop, no issues, 60hz is available
- When the monitor is connected the SD25TB4 via DisplayPort, no issues, 60hz available

I have confirmed that:

The monitor is connected via an HDMI 2.1 Ultra High Speed cable, capable of 8K
The Dell dock has the latest firmware
The laptop has the latest display drivers

I have tested this with another monitor connected to dock, a later LG model that and have the same results.  
I have tested this with two other computers connected to the dell dock, same results

For some reason, the HDMI port on the SD25TB4, will not output 4k@60hz and I'm out of ideas, other than thinking something wrong with the dock

Reaching out to Dell support, but also posting here in case there are other ideas.  I want to use HDMI instead of DP as a personal preference.