When deleting a node from the recycle bin, Umbraco will try to load the recycle bin root node by going to -20 -> /umbraco#/content/content/edit/-20
That returns a 404 though, as in newer versions the node id apparently needs to be recyclebin -> /umbraco/#/content/content/recyclebin
Tested on version 7.10.4 and 7.12.2
@sniffdk well spotted!
PR in #3843.
Thanks Mads! And thanks Kenn for creating the PR to go with this. 馃憤