Tested MCP1700-3300E dropout voltage doesn't match datasheet
The first thing I would check is how it works if you use the recommended decoupling:

This from the datasheet link you posted.
Without the decoupling, the LDO may oscillate and not give the correct DC voltages.
Also note they use ceramic capacitors - it may not work if the ESR does not meet the requirements - see sections 5.1 and 5.2 in the datasheet.
Most voltage regulators are critical about the decoupling - LDOs with low drop out are particularly demanding - always read the datasheet.