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.

A couple of things to think about which may help. Firstly I would do a drift test to check your AeT estimation from the MAF formula. If you’re a runner you could do it on a local track since you don’t have treadmill access. That would at least eliminate one possible problem if the Drift test AeT and the MAF estimation are close. Another thing that jumps to mind is how quickly you respond to the training stimuli vs your training volume. If I am reading correctly you are doing 4+ hours of total sub AeT work per week. At this volume I would expect to not see very dramatic changes until 3-6 months of consistent training and quite possibly longer if you happen to be someone who doesn’t respond particularly quickly, were all a bit different in that regard. FWIW I have seen a fairly big difference in rate of initial improvement between those athletes doing 4-6 hours per week and those in the 10-12 range. I totally understand not everyone has the time/need/desire to put in the higher volumes but the lower volume training needs to come with the realization that the adaptations will take more time.