I too have this very same issue on occasion. I cannot seem to reproduce the issue consistently, it always just sort of happens, or rather I notice it, when I’m no longer on my saved WiFi and am solely connected to LTE.
I always dismissed this as part of an ongoing series of connectivity issues I’m experiencing for years now based on my understanding that my carrier, T-Mobile, has for some years now made the explicit switch to IPv6 only.
This incorrectly asserted the problem was with my carrier as sometimes when I switched off the VPN (which for a good chunk of time it was AdGuard before settling with Blokada) but when the issue persisted and for a time I thought maybe it was AdGuard causing it, I was forced to find alternative causes… Which led me straight to DNS being at the crux of this ever bugging issue.
What I found with Blokada that was different than AdGuard was that disabling VPN on Blokada actually seemed to turn off and sometimes connectivity was restored within seconds. Where on AdGuard it often seemed disabling it would require a device reboot in order to “deregister” or “clear” the connection bug.
So my issue still stands. I’ve tinkered with all the Blokada options, some more stable and showing promise of being a solution. But I’m still scratching my head as to what exactly is causing it. Is it certain DNS hosts, or just any use of any third party DNS host? Or is it at all related to encrypted connections? Does it happen only when my phone without my noticing continually connects/disconnects from my WiFi AP forcing some sort of “time out” or perhaps it’s filling up some memory cache buffer or address table which after a given time will create problems reestablishing some network connections? I’d love to know or be guided to a better methodological approach to troubleshoot this once and for all!