This part is the inlet part of an axial fan. Just after this part, you have the rotating part then an outlet zone with a “rectifier” (not sure regarding the translation).
The same issue appear on the 3 parts.
May be we see on your picture the differents areas from the decomposition ?
The transformation looks good but the issue is that the cells are still connected (topology is preserved). It means that there are cells between the two sides of the unfolded cylinder.
One solution is to use two clip filters (one is inverted) to “cut” the cylinder, then apply the transformation with the calculator: