Edit: Missed that the statement was a quote from a previous answer.
What was not reliable? In throughput? In link drops? In packet retries? Was that all constant or changing over time?
What AP and antennas did you use?
Did you align the antennas? How?
Do you have the metrics on the achieved signal strengths & interference level on both ends when the link was up? If you have low SNR, higher gain antenna or better alignment may work.
What channels did you use?
Did you see DFS channel changes?
Did you do a spectrum analysis on both sides of the link to see if the spectrum was clear and which are the best channels to use?
Did you do a link-budget calculation with your antennas and APs?
The solution is as enterprise as you can have. Longer distance point-to-point need to be carefully designed, and depending on the exact requirements you can implement such a design or not.