Looking at https://test.wikidata.org/w/api.php?action=wbgetentities&ids=Q17&format=jsonfm, some claim GUIDs are starting with an uppercase Q, others use lowercase Q.

Trying to remove two claims using different cases will throw an error:

Request (via APISandbox): summary=testing%20bug&token=TOKEN&claim=q17%245559fec3-49b7-2160-88bd-d5c5447bb1fb%7CQ17%243273c6cf-4355-f34c-f212-28d2ff40fe57

{

"servedby": "mw1148",
"error": {
    "code": "invalid-guid",
    "info": "All claims must belong to the same entity"
}

}

If you try to uppercase an id that is lowercase or vice versa, you'll get:

{

"servedby": "mw1195",
"error": {
    "code": "invalid-guid",
    "info": "Claim with guid Q17$5559fec3-49b7-2160-88bd-d5c5447bb1fb not found"
}

}

Either some kind of maintenance script needs to be run uppercasing all the ids (better), or wbremoveclaims should be patched to ignore case (easier).

Version: unspecified
Severity: normal