New customer, works from home through Global Protect VPN. Since change to X, I have connection/VPN dropouts that disrupt data transfers

I am a new/old customer of X. I work from home for a sizeable company with a dedicated IT department and we must connect to our network using Global Protect VPN

Switched back to X 3 weeks ago and from the start, when attempting to upload data to our network, the internet or gateway or VPN drops out and fails the data transfer. Normal video calls, downloads, and other high-bandwidth activities are perfect. As are all other connected devices on same gateway. Its only an issue on data upload to network. 

I've performed diagnostics on my own as well as with company IT. Performed all the networking 101/201 stuff and then some.

• Reboot devices (all)
• disabled advanced security
• Update drivers
• Created dedicated 5ghz network just for computer
  • to eliminate the auto-switching setting in gateway
• Update OS (windows 11)
• tried on ethernet vs wifi
• Changed VPN locations, we have two
• tested on other wifi networks and all worked as expected
  • Mobile hotspot
  • Neighbor
  • Hotel during work travel
• Company IT claims to have checked everything on their side
• Googled Global Protect VPN and Xfinity
  • Thats a laundry list of problems
  • No solutions

Nothing changes

I was a customer 5 years ago and switched due to price. At the time of the switch, all computer/VPN details were the same as they are today. 
All previous ISP and gateways worked, as well as any other wifi network works

On phone with Xfinity L2 support for over an hour. Best he could offer was a gateway restart (told him I've done that multiple times) and kept saying speeds are find. He's pointing the problem at my IT or Global Protect, while my IT is pointing at Xfininty. L2 support would not honor my request to escalate but offers no level of details to suggest why this problem is occurring, other than "we don't support VPN troubleshooting" to arm me with the information needed to push back on my company IT. Company IT says "there is something wonky with the "auto-switching" and/or the packet maximum transmission unit (MTU) size. Push through L2 and explain this"

L2 rep ultimately REFUSED to escalate regardless of my challenge to go beyond basic level diagnostics as well as a request to monitor my traffic during the data transfer attempts to observe for unusual activity. 

How can I escalate this to a technical support level beyond the standard gatekeepers to obtain definitive details which supports their claim that the problem is not Xfinity nor X hardware. I am considering purchasing 3P modem/router but only as a last resort