Hi! try to re-format your SD card  to be portable storage (not internal storage) and report back if this fixes your issue. Same issue with me. Memory card as internal storage: failed update. Then formatted as external, tried OTA again and: finally it worked.  :D But now i have to bring back...

updated to 20170414 and also feeeling the softwarebuttons (home, back, menu) very hard tu use.

This should be fixed in future update please.