When flipping some schematics symbols (e.g. MOSFET) to mirror them, the pin numbers do not flip and thus end up overlaying pin names. See the screenshot below which shows mirrored symbols on the right and their corresponding un-mirrored ones on the left.
The MOSFET symbol is a bit special in that the pin names are texts to get their placement right. You can use orientation-specific text placements to fix this issue. PRs are welcome.