Steps for downgrade:
- First download 0000 firmware of your need there (available J ones: T-HKMDEUC, T-HKMFDEUC, T-HKPDEUC, T-N14MJDEUC):
https://mega.nz/#F!SxgEjAiI!cnvb1JXlhvxlsKKRml5K0A
Mirrors:
https://yadi.sk/d/jM_jtM9fmYaB3
https://yadi.sk/d/vzFyDJP7n7rDk
Install it following usual Samsung official procedure for USB upgrade:
2015 TV Firmware Upgrade Instructions - Then repeat upgrade procedure with any other version of your choice. Has been reported that upgrade might take several tries from TV menu to start.