Solidify Modifier going in all directions

I was trying to create a different version of a stylized archway. I used a couple of bezier curves to get the basic shape then borrowed some of the shapes from the original archway. I got everything lined up, then joined the mesh created from the curves to the shapes from the archway. Then I painstakingly went thru and connected the shapes to the curve and then used F to fill them in. Then I removed the original shapes by separating as I wanted holes there and tried to solidify the results. Oh lordy, I did something very wrong somewhere because this is not what I was expecting. In the video, I show my mesh and what it does and then the original exhibiting the desired behavior.