The "fix" for this issue, if you want to call it that, is 7-person mechanics.
To put it otherwise: 5-person mechanics, like 2-umpire mechanics in baseball, involves a series of compromises in order to have eyes on as many plays as possible. Unfortunately, a few fall in the gaps.
When that happens, we make the best of it. Not much of a fix, I'll grant you, but it should offer some comfort to realize that "making the best of it" here is not a defect of the official(s) but of the system.