Hi.
We aren’t able to reproduce. It’s little looks like when you have monitor unplugged – desktop isn’t detected somehow and then you are creating a new desktop during connection. Because physical exists and you are created a new one with the same user – browser is opening on other display (or just cannot be open on this display). Is could be the case?
Please try Tip 2: Connecting to a headless Raspberry from article: https://www.nomachine.com/tips-on-how-to-set-up-your-raspberry-pi-for-remote-access-via-nomachine
Edit RPi config file sudo vim /boot/config.txt, find, uncomment and set key: hdmi_force_hotplug=1. Save the file and reboot device.