When a shard is to be snapshotted, we acquire a store ref (wrapped in an index commit) and then enqueue the shard snapshot task for execution by the repository:

https://github.com/elastic/elasticsearch/blob/b124763772748d8993911e4a7ba94b17472a9539/server/src/main/java/org/elasticsearch/snapshots/SnapshotShardsService.java#L369-L384

If the shard is closed while its snapshot is in the queue then it looks like we do not release the store ref promptly. Instead, we keep hold of it until it reaches the front of the queue, which could be many minutes later. During this time the shard cannot fully shut down and release the shard lock, leading to a `ShardLockObtainFailedException` being thrown on attempts to reinitialise the shard.
server/src/main/java/org/elasticsearch/repositories/blobstore/BlobStoreRepository.java
}
    // 
    RateLimiter getSnapshotRateLimiter() {
        Settings repositorySettings = metadata.settings();
        ByteSizeValue maxConfiguredBytesPerSec = MAX_SNAPSHOT_BYTES_PER_SEC.get(repositorySettings);
        if (MAX_SNAPSHOT_BYTES_PER_SEC.s(repositorySettings) == false && recoverySettings.nodeBandwidthSettingsExist()) {
            assert maxConfiguredBytesPerSec.getMb() == 40;
            maxConfiguredBytesPerSec = ByteSizeValue.ZERO;
        }
        return getRateLimiter(
            snapshotRateLimiter,
            maxConfiguredBytesPerSec,
            MAX_SNAPSHOT_BYTES_PER_SEC.getKey(),
            recoverySettings.nodeBandwidthSettingsExist()
        );
    }
    // 
    RateLimiter getRestoreRateLimiter() {
        return getRateLimiter(
            restoreRateLimiter,
            MAX_RESTORE_BYTES_PER_SEC.get(metadata.settings()),
            MAX_RESTORE_BYTES_PER_SEC.getKey(),
            true
        );
    }
    @Override
    public long getSnapshotThrottleTimeInNanos() {
        return snapshotRateLimitingTimeInNanos.count();
    }
    @Override