Reproduction (while creating and removing a statement with no page reload:
- Create an item
- Create any statement & save it
- Try to remove the statement
- You'll receive the error message
Other reproductions are possible, and I guess this will work for any cases when you create and save a statement and then try to change it in any way without reloading the page.
On Items the updated baserevid is used.
Network requests:
The request to create the statement was:
```
action: wbsetclaim
format: json
claim: {"type":"statement","mainsnak":{"snaktype":"value","property":"P730","datavalue":{"type":"wikibase-entityid","value":{"id":"Q365815"}}},"id":"L11$ca0a13c9-424d-0a4e-c8c7-53a39bd870d1","rank":"normal"}
baserevid: 1002877
bot: 1
token: XXXX+\
```
With response:
```
{"pageinfo":{"lastrevid":1002878},"success":1,"claim":{"mainsnak":{"snaktype":"value","property":"P730","hash":"ad5cce903831858c590742e23a8e808227e5ae71","datavalue":{"value":{"entity-type":"item","numeric-id":365815,"id":"Q365815"},"type":"wikibase-entityid"},"datatype":"wikibase-item"},"type":"statement","id":"L11$ca0a13c9-424d-0a4e-c8c7-53a39bd870d1","rank":"normal"}}
```
And the remove request was:
```
action: wbremoveclaims
format: json
claim: L11$ca0a13c9-424d-0a4e-c8c7-53a39bd870d1
baserevid: 1002877
bot: 1
token: XXX+\
```
With response:
```
{"error":{"code":"invalid-guid","info":"Invalid claim guid.","messages":[{"name":"wikibase-api-invalid-guid","parameters":[],"html":{"*":"Invalid claim guid."}}],"*":"See https://wikidata.beta.wmflabs.org/w/api.php for API usage. Subscribe to the mediawiki-api-announce mailing list at <https://lists.wikimedia.org/mailman/listinfo/mediawiki-api-announce> for notice of API deprecations and breaking changes."},"servedby":"deployment-mediawiki-09"}
```
Reloading the page and removing again succeeds with the following request:
```
action: wbremoveclaims
format: json
claim: L11$ca0a13c9-424d-0a4e-c8c7-53a39bd870d1
baserevid: 1002878
bot: 1
token: XXX+\
```
**Note: the updated baserevid**
Screencast (for statement creation and removal):
{F18134007}
Screencast (for a similar action, creating a statement then trying to add a reference):
{F18134052}