Here's an interesting case.
I was not machshir this mezuza for a few reasons.
In this mezuza you have instances of a vav with the same dimensions, in some locations (ואספת, ושמתם) it's a vav and in others it's more of a nun (יורה). Its hard to tell because in the word יורה for instance - is the hey long or is the reish short? We know that bediavad the regel of a reish can be kosher if its the size of a regel yud. But, the yud here is even shorter than the reish. Without the hey, the vav would be a clear nun.
But if we call the vav a vav based on the height of most of the rest of the line, then the nun of פן should be a zayin even though normally פן is a unique case due to the height of the peh.
There are similar instances with other letters, eg kafim etc
Normally we look at both dimensions of a letter and the surrounding ktav. In this case the surrounding ktav changes drastically between lines and even words.