Your Surface Pro 11 (Snapdragon) has to squeeze 5120×2160@60Hz through DisplayPort using DSC (Display Stream Compression) or MST tiling. Going through the Dock 2 adds an extra DisplayPort tunneling hop, and the Adreno GPU driver has to renegotiate that link/DSC handshake through the dock — that renegotiation is your 1–3 sec black screen. Direct connection skips that extra hop, so it's stable. Your old Intel Surface's driver stack just handles that same renegotiation faster/cleaner.
Not an official/documented Microsoft bug with a firmware fix — it's a broader known weak spot with Snapdragon X + docks + high-bandwidth display modes, not something Dock 2 firmware has specifically patched.
- Temporarily drop to 4K or disable HDR/force 8bpc on the monitor — if flicker disappears, confirms it's DSC/bandwidth renegotiation.
- Check for a monitor firmware update (very common fix for 5K2K panels + docks).
- Look for an MST/tiled vs. single-stream toggle in the monitor's OSD.
- Turn off any auto refresh-rate/power optimization for that display in Windows Graphics settings.
- Manually update the Adreno graphics driver from Microsoft's Surface Pro 11 driver page (not just Windows Update).
- If still unresolved, escalate to Microsoft support with your clean repro (old Surface fine, new Surface direct fine, new Surface + Dock 2 flickers) — it's isolated enough to warrant real investigation.