I've noticed a strange random JS error on onepagecheckout. Randomly I read this error in console and executions of submit order stops
> POST /onestepcheckout/index/savePost/ 503 (OK) send @
> ma.jq.slide.js:4 f.extend.ajax @ ma.jq.slide.js:4
> $.widget._placeOrder @ opcheckout.js:418( anonymous function) @
> jquery-ui.js:401 $.widget._save @ opcheckout.js:569 (anonymous
> function) @ jquery-ui.js:401 (anonymous function) @ opcheckout.js:105
> f.event.dispatch @ ma.jq.slide.js:3 h.handle.i @ ma.jq.slide.js:3