I spent the last day going crazy trying to figure out why my prints were having trouble sticking (or even really seeming to extrude) during the first layer. I thought maybe I had hit a defective portion of filament and tried different ones. I thought maybe my BuildTak surface was "contaminated" somehow by oils from my skin from me touching it, but replacing it with a new BuildTak did nothing.
When prints first start the printer barely seemed to be extruding, essentially just putting out tiny spurts here and there. After trying the stuff above, I thought maybe my printer itself was having issues and tried to manually push through the filament, and saw that actually worked, so I ended up printing the full first layer with my manual help on the filament. But then I saw that the second layer printed perfectly fine without me helping. That gave me a hunch that it was maybe related to the new 4.1 software. Long story short, reverting back to 4.0.1 fixed the first layer issue.
So this post is mostly a heads up to anyone seeing the same thing, and also hopefully to the developers, to whom I'm happy to provide my gcode files if they would be useful in tracking down the bug. Also, for what it's worth, I have a Flashforge Dreamer.