BIQU Cryogrip Glacier lost grip in a couple of months... was it my bad?

I was really happy with this build plate at first... I had easily switched from printing at 60°C to 45°C and adhesion was perfect every time, even for small parts without a brim.

Now, however, after a couple of months, I’ve had to gradually raise the temperatures back again, and I still often risk print failures with certain filaments, like PLA Silk.

What do you think happened? I use 70% isopropyl alcohol to clean it after almost every print; could that have damaged it?

I got another identical plate, it works perfect right now but I'm afraid it will meet the same fate very soon, if I don't figure out the cause