Many "Failed to delete key from cache on callback" messages

I see a large number of these, but my caches are big and not so heavily used, so they seem a bit out of place.

025-10-26T17:13:38.579944Z  INFO nativelink_store::existence_cache_store: Failed to delete key from cache on callback, store_key: Digest(DigestInfo("f54f8dd70fc6b2f99bac1a5ef868f454fd9619c837e2b1077f61cb100d56b5ac-197"))
at nativelink-store/src/existence_cache_store.rs:81
in nativelink_store::filesystem_store::filesystem_store_emplace_file
in nativelink_service::bytestream_server::inner_write with digest: DigestInfo("f31a04270c78a5c0313f140affb15804aa803500f8f8a53acda9af254b16ae38-87654143"), stream: WriteRequestStreamWrapper { resource_info: ResourceInfo { instance_name: ">
in nativelink_service::bytestream_server::bytestream_write
in nativelink_service::bytestream_server::write with request: Streaming
in nativelink_util::task::http_executor
in nativelink::services::http_connection with remote_addr: 192.168.191.220:64842, socket_addr: 0.0.0.0:50051

Start at nativelink-store/src/existence_cache_store.rs:81 and trace the callback from filesystem_store_emplace_file through the bytestream write path shown in the report. Determine why cache-key deletion fails and verify the fix against the reported logging behavior and cache usage scenario.