Just another member so take this with a grain of salt but it feels like more information might be needed.
1) How did you establish your AeT?
2) Have you done retests along the way/recently and do you see any progress there?
Comparing performance at AeT over time would be what I would use to judge progress.
My mental picture of this is that your previous fitness developed a high degree of fitness above AeT over the course of years so you had developed some degree of efficiency when operating in that zone, but you only have a couple months focusing on similar development of AeT which might unsurprisingly be less efficient.
For me this is why I found the combo of regular (once every 2-3 months) AeT and AnT tests really useful. What I observed personally when shifting to an AeT focused approach was a slow but steady improvement for AeT pace/HR and an initial drop in AnT followed by improvements of pace/HR at AnT in the mid/long term. If I remember correctly I returned to similar pace/HR for my AnT tests around the 4-6 month mark and saw notable improvements closer to the 9 month mark.