We're interested in your Pi-hole container's configuration parameters.
That only means that they would deliver DNSSEC signed replies.
Validation is handled among Pi-hole and the respective DNS server authoritative for a requested domain.
Pi-hole would verify that DNS replies have not been manipulated by third parties, by checking the cryptographic signature against the DNS server authoritative for the requested domain.
If an authoritative DNS server is capable of digitally signing its DNS records (i.e. it supports DNSSEC), then Pi-hole will check them and only mark the replies as SECURE and deliver them to clients if they pass DNSSEC validation.
If they fail DNSSEC, Pi-hole will discard the replies and mark them as BOGUS, i.e. a client can't resolve that domain.
If an authoritative DNS server is not supporting DNSSEC, Pi-hole can't apply DNSSEC validation. Pi-hole will mark such replies as INSECURE and deliver them to clients.
For further details, see also Understanding DNSSEC validation using Pi-hole's Query Log.
You could, but you'd sacrifice some trust if you switch off DNSSEC, as Pi-hole would not validate DNS replies at all.
From the details you've shared so far, it's not evident whether DNSSEC would have told you that some DNS replies can't be trusted.
We'd need more details to answer that.
How did those failed requests register in Pi-hole's Query Log?
Note that DNSSEC validation would require accurate time information on the machine hosting Pi-hole, or else all checks would fail.
It is unlikely that your time is inaccurate, as you are only observing resolution failures for some polish domains, but it's worth checking nevertheless.
Even with accurate times, sporadic failures for very short periods are to be expected, e.g. when an authoritative DNS server is down for maintenance, or if it has been updating its public keys used for digital signature, but DNS replies as cached by upstream resolvers would still be signed with the previous key.
Usually, such failures should go away after a short while.
And finally, we've received a similar report about .pl domains a while ago, where public DNS adjustments seem to have been causing temporary failures, see DNSSEC resolving problem with .pl domains - #14 by s.beimer.