Why do circuit diagrams at certain airfields keep appearing and disappearing in chart updates? Elstree EGTR being an example where every now and then, the circuit diagram will appear following a chart update only to be removed the following chart update. Why would this keep happening?

You would need to contact customer support to enquire about a specific airfield's update history. They might be able to give you an answer but I certainly can't.

This seems a strange response being that my question was more generic and I had cited EGTR as an example. Back to my original question and perhaps let me rephrase: What dictates Circuit diagrams being depicted and then to subsequently be removed? Happy to raise a support ticket with regards the specific example of EGTR