I'm still working just not that much as before.
The builds are saved in cookies and it's weird, I didn't changed anything except a name of a weapon in the past days and all the saved to test stuff builds here aren't affected ._.[technically only the ids are saved so there is no problem with name changes I think, I will double check them when I've time].
Here it works fine in Chrome, IE[with his limitations] and Mozilla[the browsers I use to check stuff].
Which classes had you saved there and which what gears if[+/-]? If you remember it ofc, may be a class specific problem.
The 400 error usually means something bad on your side >>click<<
or maybe the server gone crazy from nowhere dunno[it's a free hoster so nothing super perfect :|], could also be some random error with something[if you get the error again check with which item/buff were you "toying"].
If you've the links I can do a check to see if there is anything wrong with them[you can pm me if you don't want to share the builds in public].
If you want to test one made just now to see if you still have error or is something in your side >>click<<
Did you tested it with any other browser?