Many plants uses ethanolamine to increase the pH for MEG. It is because the H2S and CO2 causes the decrease of pH and ethanolamine dissolve them and you can recover it heating
You are having something different. You must look for a component to stabilize your MEG pH. But without knowing the restrictions for your plant, it is hard to give options.
So, my suggestion first is to clean your MEG with ethanolamine and after correct the pH with a organic weak acid. At first your pH will raise and then you can control it dropping with the acid.
Hope it helps you.