I cannot reproduce the issue. But... now the panning only possible after the zoom in. Previously it was possible after zoom out too. Of course, the Preview Scaling needs to be set to Output or to Canvas. Or maybe I miss something.
This is what I'm seeing, too, with 29.1.1 (64-bit) for Windows.
SPACE+MWHEELUP to zoom in, then left click while still holding SPACE to reposition. I cannot reposition after zooming out (SPACE+MWHEEDOWN), which makes this very tricky to get right.
I'm not 100% certain what the behavior used to be, as I'm new to OBS Studio, but it appears to have been possible to zoom out and then reposition at some point in the past (based on old video I found). If that's true, this seems like a regression.