I'm facing the same issue on 6.48.1
Before issue occur I added 22k static dns records to setup smth like ad block functionality. Had only 27 mb RAM available after that.
Normally, before import, ~100 mb RAM was available (lovely days) which means that import resulted in permanent loss of 73 mb of ram.
Looks like memory leak. Tried to flush dns cache but operation was failed due to timeout. Several tries after and one finished w\o errors but cache was not cleaned actually.
Reverted everything back thanks to backup.
Last edited by Bruster
on Sun Feb 14, 2021 7:19 pm, edited 1 time in total.