Issues after Reflecting

I have been trying to follow a tutorial online and have followed it to a “T”, but I am finding when I reflect my object on the Y Axis, it is missing a number of surfaces. It is random ones as well and not symmetrical (2 on one side 3 on the other etc.) I am Currently using Rhino 7 on Mac

there is nothing one can generally suggest at this point since that is nothing that is usually happening, so might be something you simply missed? you can of course post a file.

what does that mean? “T”

“T”: I’ve followed the video step by step exactly

so there is no real explanation to it?