That shouldn’t be the issue, you have double vertices in your screenshot ( more than one vertex at the same position), which can be seen by the black dots at the edges; they are the centers of Faces, You should use A, M > Merge by Distance! (I recommend you do this even if things appear to be working correctly now.)
In fact: double vertices (solution : M > Merge by Distance) and flipped Normals (solution SHIFT+N) are together responsible for (a lot) more than 90% of all modelling issues.
