Hi everyone, I might be able to offer a small clue: I've been having the exact same DNS problem for a few months...and I don't use MBAM (sorry!).
I'm on win/64 + WiFi + Chrome + Avast (free) + Acronis ransomware protection. I do NOT update Windows (...). My Chrome sessions go crazy every few days, with many sites not resolving DNS or resolving very slowly..including Google itself. This has been happening since a few months ago, but it has become very annoying, several times per day now. For a while I thought it might be linked to using Qbitorrent and bad actors trying to attack my torrent connections. But no, even with Qbitorrent off and rebooting the system, I still get this issue. I was suspecting a corrupted Chrome add-on (it feels like a memory-leak type of bug: working fine at first, and gradually becoming worse until unusable) and started to update my usual suspects: CrapCleaner, MBAM free, etc to check if I had any problem apps.
I landed here while trying to update my old MBAM, and I am relieved to see I'm not alone. Avast be might intercepting connections and causing similar DNS errors, perhaps because of a similar defense mechanism approach? I'll go & check over there.
A few more suggestions:
1) if not a memory leak, it might be a sort of DOS attack. When it happens the browser is stuck trying to resolve sites that were loading fine 30 seconds before (eg trying to go to next page on a multi-page text), as if the DNS cache was corrupted.
2) My mobile phone which is on same WiFi has no connection problem at all, so issue is not with router or internet link.
Youtube is able to continue streaming/playing in same browser, at the same time as other sites are completely stuck resolving (doesn't make sense, but it might give a clue to someone?).
I am able to fix the problem by unplugging the WiFi USB antenna and plugging it back (flushing DNS only works sometimes and is less and less effective; removing antenna so far is 100% effective - but disabling WiFi via taskbar is not good enough. Something deep inside the OS needs to flush in order to restore the DNS resolution properly)
I'll report back here if MBAM free finds something