A similar problem:
I have 3 devices with the same Blokada + configuration:
5.14.4 / OISD / DNS encrypted / Cloudflare / Frankfurt
Samsung A40 / Android 11, Xiaomi MI A3 / Android 11, Amazon Fire HD10 (only WLAN)
Blokada app setting without battery management
On all devices, Blokada stops / blocks from time to time (even overnight). WLAN network access is no longer possible. Switching Blokada off / on solves the problem.
I have only been able to observe this phenomenon since the last version.