Does anyone know how I would fix this error?
Well, I think you're using the knit command wrong.
Knitting is for joining patches that share trimmed borders where no more than two faces share an edge. So you have to approach it like you're creating a quilt of patches. Your mirror operations have generated complete copies of the the base body and as a result you have many duplicate, overlapping faces
So your problem was your fill surface was set to merge back with your base surface.
Uncheck that and your fill becomes it's own thing. Then select all the surface bodies knit and solidify the model
Hi John, thank you for your help on this!
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