insufficient caching of some uncommon wildcards
In an NSEC3-signed zone, if a wildcard is nested deeper than directly under the apex, positive expansions from it may not be cached properly (but they succeed). Testing example:
The issue is that aggressive cache thinks it needs to additionally provide an NSEC3 record matching the closest (provable) encloser, but that's not true in this case (because the wildcard record proves encloser's existence). This NSEC3 record must exist but resolver probably hasn't obtained it, so synthesis from cache (usually) fails.
Fortunately, typical wildcard usage I see is directly under the apex
*.example.com. We may also be "saved" by queries for non-existing types on the same name (e.g. AAAA), as those need this NSEC3 record and thus the only downside would be its "unneeded" addition into the corresponding positive wildcard expansions.