As a result of the daylight activities of the MiG-23 jet fighters employed by the Cubans, artillery fire missions could only be executed at night. As it was the first time that the G5s were used operationally, there was great cause for concern that the MiGs would spot them.
The Cuban MiG-23 jets' actions during daylight hours limited artillery strikes to nighttime.  The introduction of the G5s into combat operations created a sense of apprehension that they might be spotted by the MiGs.