Only encode 15 bytes of userHandle

[deadlyrice]

Can someone confirm that this is the site's error? Because after base64 decoding the raw byte string of userHandle, the result is only 15 bytes, but the userHandle is actually 16 bytes. The user name is: yulun_test_1.

USER PRESENCE DONE.
WebAuthn navigator.credentials.get() result:
[CredentialAssertion] {
    rawId: [ArrayBuffer] (64 bytes)
        39 35 36 39 30 38 38 66 31 65 63 65 65 33 32 33
        32 39 35 34 30 33 35 64 62 64 31 30 64 37 63 61
        36 62 37 34 64 30 64 61 30 31 33 66 65 62 66 35
        38 38 34 64 62 66 32 36 35 36 61 32 62 33 37 34,
    id: [ArrayBuffer] (64 bytes)
        39 35 36 39 30 38 38 66 31 65 63 65 65 33 32 33
        32 39 35 34 30 33 35 64 62 64 31 30 64 37 63 61
        36 62 37 34 64 30 64 61 30 31 33 66 65 62 66 35
        38 38 34 64 62 66 32 36 35 36 61 32 62 33 37 34,
    response: {
        clientDataJSON: [ArrayBuffer] (156 bytes)
            7B 22 63 68 61 6C 6C 65 6E 67 65 22 3A 22 71 59
            7A 52 36 72 47 58 37 55 59 49 54 52 34 6F 39 73
            59 49 61 76 69 4E 79 68 39 61 67 49 73 75 49 45
            74 66 4E 37 4F 75 33 35 76 58 38 55 4A 32 4B 64
            77 6D 47 69 35 37 49 6B 65 79 4B 55 64 48 41 30
            4D 37 71 41 73 73 4B 35 4D 49 6A 49 62 72 78 7A
            4D 49 62 51 22 2C 22 6F 72 69 67 69 6E 22 3A 22
            68 74 74 70 73 3A 2F 2F 77 65 62 61 75 74 68 6E
            2E 6F 72 67 22 2C 22 74 79 70 65 22 3A 22 77 65
            62 61 75 74 68 6E 2E 67 65 74 22 7D,
        authenticatorData: [ArrayBuffer] (37 bytes)
            95 69 08 8F 1E CE E3 23 29 54 03 5D BD 10 D7 CA
            E3 91 30 5A 27 51 B5 59 BB 8F D7 CB B2 29 BD D4
            05 00 00 00 01,
        signature: [ArrayBuffer] (71 bytes)
            30 45 02 21 00 84 64 9C FC 5B 51 13 07 C1 F0 5E
            F0 19 57 B5 6D 13 11 93 AD DE 78 8E 37 B7 02 BA
            4F B3 BE 3D 88 02 20 11 05 C6 B5 D8 8C 85 1D F1
            FC 09 5C E6 00 57 66 BF 34 FD 32 AF 6A 8D 11 FA
            AC 7E 8B 3D 62 56 C4,
        userHandle: [ArrayBuffer] (16 bytes)
            FF B1 1B B9 68 3D DA 5E B6 91 85 F7 2F 61 13 F6,
    },
}

Sending Message to Server:
>>>>>>>>>>>>>>>>
{"rawId":"OTU2OTA4OGYxZWNlZTMyMzI5NTQwMzVkYmQxMGQ3Y2E2Yjc0ZDBkYTAxM2ZlYmY1ODg0ZGJmMjY1NmEyYjM3NA","id":"OTU2OTA4OGYxZWNlZTMyMzI5NTQwMzVkYmQxMGQ3Y2E2Yjc0ZDBkYTAxM2ZlYmY1ODg0ZGJmMjY1NmEyYjM3NA","response":{"clientDataJSON":"eyJjaGFsbGVuZ2UiOiJxWXpSNnJHWDdVWUlUUjRvOXNZSWF2aU55aDlhZ0lzdUlFdGZON091MzV2WDhVSjJLZHdtR2k1N0lrZXlLVWRIQTBNN3FBc3NLNU1Jaklicnh6TUliUSIsIm9yaWdpbiI6Imh0dHBzOi8vd2ViYXV0aG4ub3JnIiwidHlwZSI6IndlYmF1dGhuLmdldCJ9","authenticatorData":"lWkIjx7O4yMpVANdvRDXyuORMFonUbVZu4_Xy7IpvdQFAAAAAQ","signature":"MEUCIQCEZJz8W1ETB8HwXvAZV7VtExGTrd54jje3ArpPs749iAIgEQXGtdiMhR3x_Alc5gBXZr80_TKvao0R-qx-iz1iVsQ","userHandle":"_7EbuWg92l62kYX3L2ET9g"}}
>>>>>>>>>>>>>>>>

Received Message from Server:
<<<<<<<< [ STATUS 400 ] <<<<<<<<
{"status":"failed","errorMessage":"login failed: unable to validate userHandle"}
<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<

Error: login failed: unable to validate userHandle
Login error: Error: login failed: unable to validate userHandle
LOGIN DONE.```