ultralow hosts change from time to time

I have this weird observation that ultralow hosts change from time to time. Sometimes ultralow1 is premiumrdp-xxx, sometimes it's showing lightnode-xxx. Same with ultralow2, change from lightnode-xxx to premiumrdp-xxx. I have to manually set my private dns settings since I'm not routed to the fastest server unless I manually select which ultralow server, I connect using myid.dns1/2.nextdns.io. Is there a way to fix this?