SteamEncryptedAppTicket.BDecryptTicket does not correctly decrypt app ticket in Spacewar

[altamkp]

I am trying to create a backend server for my game built in Godot. By following this page, I have come up with the following code so far. Note that the private key was retrieved from within the example code in the sdk.

private const uint SIZE = 1024;
private static readonly byte[] KEY = [0xed, 0x93, 0x86, 0x07, 0x36, 0x47, 0xce, 0xa5, 0x8b, 0x77, 0x21, 0x49, 0x0d, 0x59, 0xed, 0x44, 0x57, 0x23, 0xf0, 0xf6, 0x6e, 0x74, 0x14, 0xe1, 0x53, 0x3b, 0xa3, 0x3c, 0xd8, 0x03, 0xbd, 0xbd];
    
public AuthenticationResult Authenticate(string ticket) {
    var ticketEncrypted = Convert.FromBase64String(ticket);
    var ticketDecrypted = new byte[SIZE];
    uint ticketSize = SIZE;
    if (!SteamEncryptedAppTicket.BDecryptTicket(ticketEncrypted, (uint)ticketEncrypted.Length,
            ticketDecrypted, ref ticketSize, KEY, KEY.Length)) {
        return new AuthenticationResult(false, null!);
    }

    return new AuthenticationResult(true, "Hello world");
}

My problem is that SteamEncryptedAppTicket.BDecryptTicket always return false. The documentation for this api states that it returns false under these conditions:

false under the following conditions:
cubKey was 0.
The size of the output buffer rgubTicketDecrypted is too small. It must be at least as big as rgubTicketEncrypted.
Reading rgubTicketEncrypted failed, this could happen if it's NULL or empty.
Encryption failed, likely because the key is incorrect.

Please kindly point me in the right direction.

[altamkp]

To follow up, I have discovered that further calls to other SteamEncryptedAppTicket apis return correct and expected results, even after BDecryptTicket returned false.

var isForApp = SteamEncryptedAppTicket.BIsTicketForApp(ticketDecrypted, ticketSize, (AppId_t)480);
var appId = SteamEncryptedAppTicket.GetTicketAppID(ticketDecrypted, ticketSize);
var issueTimeUnix = SteamEncryptedAppTicket.GetTicketIssueTime(ticketDecrypted, ticketSize);
var issueTime = DateTimeOffset.FromUnixTimeSeconds(issueTimeUnix).ToLocalTime();
SteamEncryptedAppTicket.GetTicketSteamID(ticketDecrypted, ticketSize, out var steamId);

If the above calls return correct results, I would expect that the ticket was successfully decrypted. Could this be an issue related to #21?