Thank you, @Pliny!
Ah yes, that happens sometimes when the stitching of the buttonhole is very tight, making it too stiff. More likely to happen with lighter fabrics, probably. That jacket sure looks like a 3r2 to me. Perhaps that buttonhole will loosen up a bit over time, is it a new jacket?
I've had it for a bit over a year, but sparingly used. Hopefully will loosen up, but to be honest, I'm not all that bothered. Love the fabric over anything else.