Reviving frozen milk kefir troubleshooting help

I had previously frozen some kefir for backup. It was in the freezer for several months. I recently needed and brought it out to wake it up. Been feeding it raw milk for a month and a half. The grains seemed to not want to grow for the first few weeks but it has been showing signs of growth at an extremely slow pace. The main kefir I had before grew so fast that I didn't know what to do with the excess. I left that one for 2 long without feeding and it died.

I've been trying 72hr ferments, which is the longest I would ever let it sit. By this time, it usually separates into curds and whey, but it hasn't been doing so. Oddly though, the milk does thicken and has a little tanginess to it. It doesn't taste bad at all. In Fact, I like it. Maybe some bacteria strains are completely dead and this form of kefir isn't as powerful as my regular kefir?

Any thoughts?

Leo, welcome to Permies!

I have frozen milk kefir grains successfully, but I don't recall how slow or quick they were to get working again. Any time I change the kind of milk I'm using, I almost always experience a slow-down in production with the grains. But eventually (some times weeks) they come around.

How is your room temperature? We're in a cooler time of year, could that make a difference?

I don't like freezing grains for this reason. They recover better after drying.

I've experienced something similar when I tried to keep the grains in water every other batch. Like, if they don't feel at home, they don't grow. And it tastes more acid than usual.
While it recovered, I used the curd for making labneh.