Guild Task - No reward

Platform, device version and operating system:
PC, Windows

Screenshot or image:

What you were expecting to happen, and what actually happened:

I went to my mail to claim my task rewards, and found that many rewards, are claiming that I claimed them from another guild, and am ineligible for rewards as a result. I have not changed guilds, and have been a part of the same guild for weeks. I submitted a ticket which was closed with no action or communication.

How often does this happen? When did it begin happening?

This happened today, and it is the first time that it has happened that I am aware of.