Comment # 1 on bug 923491 from Bernhard Wiedemann

Try zypper ref
to refresh the repo metadata.

Sometimes it happens, that you load the metadata
which tells that there is version 261
but then the repo gets updated to only have version 263
thus zypper tries to load version 261 of the rpm but can not retrieve it

This could be avoided either in zypper to do one auto-refresh in this case
or by OBS to not delete old versions immediately.