Suddenly, all payment methods are not shown in checkout. I have a custom payment method together with bank transfer payment, and none of them appears in checkout.
What may be happening?
Finally, it was due to incorrect checkout_index_index.xml that existed in my Magento_Checkout folder.
I am having the same error again, but in this case could be due to another xml file.
This error appears in system.log:
[2016-03-16 14:29:24] main.INFO: Cache file with merged layout: LAYOUT_frontend_STORE1_56f1b068ec7ccf4878f9284dd1137afd1: Please correct the XML data and try again.  
In this case, I cannot find out where the error is.
Can you help me please?