Steps to Reproduce:
Follow the link https://en.wikipedia.org/wiki/Special:ApiSandbox#action=query&format=json&prop=linkshere&titles=Ashmolean_Museum&lhnamespace=4&lhshow=!redirect&lhlimit=500
and click "Make request"
Actual Results:
The sandbox link initially strips out the last three parameters from this URL. The Request URL shown in the form stops after &titles=Ashmolean_Museum . So the query run in the API sandbox is different from that intended.
Going directly to the API, this problem does not appear:
https://en.wikipedia.org/w/api.php?action=query&format=json&prop=linkshere&titles=Ashmolean_Museum&lhnamespace=4&lhshow=!redirect&lhlimit=500
Paste the missing parameters onto the end of the Sandbox API URL and click "Make request" again, and the query runs as intended.
Same problem occurs on Commons: https://commons.wikimedia.org/wiki/Special:ApiSandbox#action=query&format=json&prop=linkshere&titles=Institution:Ashmolean_Museum&lhshow=!redirect&lhlimit=500
This query is truncated after &titles=Institution:Ashmolean_Museum .
These API Sandbox links are generated by the {{ApiEx}} template on MediaWiki.org. See https://www.mediawiki.org/wiki/User:MartinPoulter#Incoming_links_to_a_Wikipedia_article,_excluding_redirects,_from_pages_in_Wikipedia:_namespace
Expected Results:
The API sandbox should execute the same query as the direct link to the API, with all the parameters, without needing to be reloaded.