Hi... have worked on a few E4412s... and have found that most E4412 fails (failing specs) are due to something physical... Most times internal RF connector needs to be taken apart and cleaned. I normally use a carbon eraser (pencil type) to remove all the black "carbon" and dirty marks. Normally takes me about 15 minutes. Reassembly can be tricky, but practice helps (has helped me). There are pins and isolators that normally need cleaning; normally use a magnifier (x7) to find the dirt (or problem).
Just be careful, there some very small parts in the RF connector, especially a very small bellow next to the RF microcircuit, this bellow is about 1mm. I normally work on a bench, over a blank plain white sheet of paper.
Example, today checked 4 E4412s, one was failing at about 6 GHz (was about 6% low)... after cleaning the internal hardware (took RF connect apart). After cleaning and re-assembled, sensor was within about 1%. Other tech (I showed this to, could not believe it)... just saying... it is not always an adjustment... sometimes it needs a repair action.
Hope this helps...