Sorry for the late reply. I just took a short break from counting calories. First of all, I'm in no position to give any kind of advice, I am just figuring things out myself by trial and error. But I think I've been through what you are going through at the moment. After hitting plateaus that last for weeks, for the last several months I've been doing intermittent fasting and I have reduced my weekly caloric deficit to 1800Kcal from almost 8000Kcal. Some days I consume maintenance calories (around 2100kcal). I try not to have a caloric deficit of more than 500kcal a day. The side effect of being on a significant caloric deficit for a long time is a slow metabolism. Basically, your metabolism and BMR adapt to your new eating habits despite what the app says. But the good news is that the hard part is over. It seems you've already trained yourself to be on a significant caloric deficit. What I do at the moment is a lot easier than what I thought I should do. Good luck!!