Contact list avatar issue

I have just experienced a very strange issue with the spark roster.

I am experimenting with adding avatar images in the jpegPhoto field of our LDAP directory.

This was all working fine until suddenly things went wrong.

For every user using Spark 2.5.6 started seeing the same avatar for all users in their contact list who don’t have an avatar and were using the same version of Spark.

I personally was using a later version of spark 2.5.8 and was unaffected.

Users using other IM clients were unaffected.

Users where the avatar image was set were unaffected.

Very strange. I repeated it with a version of Spark 2.5.6. Then I restarted the server and cleared out my local Spark folder and things have returned to normal for now

Any ideas anyone? We are using a skinned version of the Spark 2.5.6. But I might press to replace this with the vanilla 2.5.8.