Fail to upload changes in relations

[anonymous]

When uploading changes in relations I get the following error: "Transfer aborted due to error (will wait for 5 seconds): 412 precondition failed".

That means I cannot do changes in relations other than splitting ways that is member of a relation, I cannot add or remove members of a relation.

The problem might be API, though I doubt it.

[anonymous]

This means the API could not validate your change and refused it. What relation do you talk about?

[anonymous]

It is a road relation in Brazil, BR-116, relation 62899.

[Mapper]

This can happen if at least one member of the relation has a problem. One case is easy to reproduce:

• user A and user B download the same relation
• user A deletes a member of the relation and uploads it
• user B does changes on the relation and uploads it
• the already deleted member is again part of the relation --> this causes the error mentioned above on the next upload

This happens quickly with relations containing lots of members and will be eliminated with API 0.6. It is not a defect of JOSM.