As the lunar module approached, Young saw it through his sextant at a distance of 259 kilometers. Stafford and Cernan got a radar lock on the command module shortly after the insertion burn and watched with interest as the instrument measured the dwindling gap between the vehicles and demonstrated the theories of orbital mechanics in actual practice. Cernan especially liked the steady communications that kept both crews aware of what was happening.
The abort system had two basic control modes, “attitude hold” and “automatic.” In automatic, the computer would take over the guidance and start looking for the command module, which was certainly not what the crew intended to do at that moment. While correcting for a minor yaw-rate-gyro disturbance, the astronauts accidentally switched the spacecraft to the automatic mode, resulting in frantic gyrations.
When Stafford and Cernan were ready for undocking they discovered the Lunar Module had slipped three and a half degrees out of line with the command module at the latching point, possibly due to loose mylar collecting on the docking ring…
At first stage cutoff the astronauts expected to encounter a single pulse of negative G and the crew would be thrown forward in their straps before the Second stage ignited and recommenced the acceleration. However, they actually encountered a form of pogo which continued for 4 cycles, during which they were “slammed forward, back, forward, back, forward, back, and forward, back. At this point the instrument panel was so blurred the astronauts could not read it.