Hey yo, @Shulyaka,
really thanks for reporting and letting us know about this. 
I just want to keep you updated. This was trully, as I thought, caused by MGLRU. Well, actually, due to some parameters, which was not exactly tweaked for us related to MGLRU as we do have a lot of RAM. That explains why users using vanilla OpenWrt on their devices do not meet it.
More details, where it is being discussed:
Once the issue will be handled there, I think the Turris guys should look into it once again because, from my point of view, MGLRU is what you want.