We store a byte[20] payload of a GUID + index using GeoAddSync. When we retrieve the payload using GeoSearchAsync, we receive the exact same byte[20] value up to version 2.13.17. When we retrieve the payload using GeoSearchAsync in 3.0.0, we receive a byte[40]. I have included a simple class that can be used to recreate the issue.

Before (2.13.17):
Assembly Full Name : StackExchange.Redis, Version=2.0.0.0, Culture=neutral, PublicKeyToken=c219ff1ca8c2ce46
Assembly Version : 2.0.0.0
File Version : 2.13.17.28173
Informational Version : 2.13.17+6e0df970c7
Original Payload
Length : 20
Hex : FEA2EECE99A4C040913416F8F5CCF4D415CD5B07

Results: 1

RedisValue.Box() Type : System.Byte[]
RedisValue.ToString() : ??????@?4??????[

Returned Payload
Length : 20
Hex : FEA2EECE99A4C040913416F8F5CCF4D415CD5B07

Payload Equal : True

Returned Guid : ceeea2fe-a499-40c0-9134-16f8f5ccf4d4
Returned Index : 123456789

After (3.0.0):
Assembly Full Name : StackExchange.Redis, Version=3.0.0.0, Culture=neutral, PublicKeyToken=c219ff1ca8c2ce46
Assembly Version : 3.0.0.0
File Version : 3.0.0.11234
Informational Version : 3.0.0+2be2ae6d7f
Original Payload
Length : 20
Hex : CC5E3DE99E279A498FCC04CF78BCB35E15CD5B07

Results: 1

RedisValue.Box() Type : System.String
RedisValue.ToString() : ?^=?'?I???x??^?[

Returned Payload
Length : 37
Hex : EFBFBD5E3DEFBFBD27EFBFBD49EFBFBDEFBFBD04EFBFBD78EFBFBDEFBFBD5E15EFBFBD5B07

Payload Equal : False

Returned Guid : 5ebdbfef-ef3d-bdbf-27ef-bfbd49efbfbd
Returned Index : 79544303