Used stamps exchanges.

Recently, I noticed that I have big amounts of blocked members (red font). I was wondering if they existed before as I didnt block anyone. Obviously, it happens autmatically. When check the list of blocked members, I noticed that they are mostly about expired or cancelled exchanges. When try to unblock some member, I get message about deleting (?) Well, quite unusual and unexpected question, since I dont want to delete anything. Why should I block someone just because exchange has expired? Confusion is more when check Home page, where some rules and conditions are presented. There is no words about blocking members after while.
So, please, give us some explanations?
Thank you.

The list with the blocked members has been there for a long time (years). At the suggestion of a member, I have made it more visible, with a red font when you have new members added from your last visit to the page.

There were several situations when a member was blocked:
When you rated an exchange with 1 to 3 (block added automatically)
When an exchange expired after 90 days (block added automatically)
Whe you use the block option from the page "Register stamps
When you cancel an exchange

I have removed the first two cases where the blocks were added automatically. Also I have removed the blocks that were added before.

Any other explanations, instructions... ?

I have also experienced this. I have to unblock members one at a time. very annoying