By 1980, the scheduled deadline for adopting the L85 and L86 was rapidly approaching, and the weapons should have been in the last stages of fine-tuning before production began. This was not the case, however - testing was still uncovering critical problems in the guns.

The goal for these weapons was 8000 MRBF (Mean Rounds Between Failure) for the LSW and 2500 MRBF for the IW. As real testing began, the numbers were actually 100-300 MRBF. In many cases, the guns could not run three magazines in a row without a malfunction, and this was literally an order of magnitude below the requirements. But what truly led to the massive problems with the L85/86 was that RSAF Enfield did not fix these problems. Instead, they moved the goalposts. With so many problems, it was decided to only count malfunctions that occurred in the endurance testing (ie, when the guns were not put under any environmental stress at all) and to only could "critical" malfunctions in the tally. A "critical" failure was one which could not be resolved by the shooter, such as a split barrel. Simple feed or ejection failures were not counted, nor were malfunctions that required gun disassembly to correct. Even under this new paradigm, MRBF over 3000 could not be achieved.

In addition, the LSW was showing a problem that would become endemic; split groups. The weapon shot very good groups in semiautomatic, but in full auto fire it would produce two discreet groups. The first shot in each burst would land about 6 minutes of angle low and right compared to the remaining rounds in the group. This would be the subject of significant work, and was never fully rectified.