The instrument on Apollo 16 was deployed but the cable from it to the ALSEP central station was broken and the experiment was rendered inoperable.

A heat flow experiment was carried onboard Apollo 13 but the mission was aborted in-flight and the instrument never reached the surface.

[2] These techniques had already established some of the characteristics of the Moon's surface including temperature, thermal conductivity and heat capacity.

[1] Further work by this group established that the probe would need to be inserted into the subsurface to avoid large temperature fluctuations caused by the day-night cycle at the surface.

[3] The cables that connect the probe to the experiment's electronics housing also have 4 thermocouples at 0, 65, 115 and 165 cm (0, 26, 45 and 65 in) from the topmost gradient sensor.

[3] The heat flow experiment was originally planned to be carried out on Apollo 13, but due to the aborting of that mission, this did not occur.

The project's principal investigator believed that if the Apollo 13 instrument deployment had been attempted, it would have led to better mitigations on later missions for the problems experienced with the drill and the compact regolith.

By this point Scott was having to apply his full weight and the decision was made to insert the first probe to prove out functionality.

[1][3] The cause of the challenges was due to the deeper levels of the lunar soil not having been disturbed for at least half a billion years.

[1] The experiment found that the very near surface of the lunar regolith, consisting of a few centimeters, was dominated by the radiative transfer of heat.

This is primarily because the material is fairly loose, with limited soil particle contact reducing conductive transfer.