tangorin is arguably the best online dictionary, but I've noticed quite a few inaccuracies – mostly invalid/missing/overly esoteric kanji readings (like ゾク & たから for 財) or deviating examples (like ゾク for again 財) – and at least one bug*.
Where can one report them? I hope it's not the forum, that would be neither convenient nor direct.
*: The "Multi-Radical Search" button is coded in such way that it becomes overlaid & inaccessible in narrow windows such as 720x1280 (standard on Android).
Tangorin is based on a database maintained by the EDRG. If you want to report inaccuracies in kanji readings etc. go to wwwjdic.com, find the entry, and click [Edit].
Tangorin uses JMdict for words and KANJIDIC for kanji, both part of the EDRDG project, www.edrdg.org. If you find errors in JMdict, then you don't need to *report* them, you can actually *fix* them. JMdict is edited through a public process. Anyone can propose edits, both changes to existing entries and new entries. If your edit is approved by one of the editors, then it becomes part of JMdict.
Before you propose any edits, it is useful if you familiarize yourself a bit with the editing process. You can follows the editing process in real time here: