Proper course of action here would be to figure out why units are phasing out of relevancy.
Read up on actor relevancy here Actor Relevancy and Priority | Unreal Engine Documentation
Debug / print those variables on a tick/timer to figure out what’s going on. Units around your field of vision should be relevant and updating.
If you want units to keep updating even when they are far away and you are not looking at them (eg. minimap), AlwaysRelevant could be an option but I suggest adding custom logic to update units NetUpdateFrequency in real time, so that units you are looking at update smoothly, while units far away update like every couple seconds on the minimap.
Alternatively, keep relevancy in but replicate just an array of locations for the minimap, which should be much lighter than replicating all the units.