Is it normal to be in limp mode and be able to shift manually on CFs?

I am amazed that cars can be running with a obvious defect and the CPU not throw a code. If the CPU is smart enough to put it in limp mode, it should have recognized a defect and the defect should have an obd number.

If it were me and I had no idea why the transmission was not shifting correctly, i would check fluid level and then replace that connector plug on the transmission. Oh and look for corrosion on any connectors.