In my experience manufacturers take a dim view of any attempted 'hack' of an equipments BIOS. They can probably see what was being attempted by the legacy corrupted data that remains in the memory chip
That is not to say that they will not repair it but in every case I have seen, the manufacturer has charged either an administration/handling fee or a 'calibration' fee. Neither is cheap and I have seen charges of between GBP50 and GBP400 quoted for such work. As soon as the OS memory area is corrupted by a user, the warranty is effectively invalidated as this is considered self inflicted unless proven otherwise. I agree that the user should not be able to accidentally damage the 1052E via RS232 but lets not kid ourselves..... Rigol knows that users are regularly attempting to hack the BIOS via this port so I doubt anyone would succeed in convincing them it was an accident.
Many manufacturers refuse to issue firmware updates. I have asked some why this is and had a similar response in each case "we do not wish to handle fault calls from users who have corrupted their equipments firmware due to poor practice or procedure". Such companies will often suggest that a firmware upgrade is normally required only if a problem exists that a later FW version fixes and the equipment should be sent to them for update and calibration.... Credit Card number please......
OT but relevant ...... I own an ICOM PCR1000 monitoring receiver that uses an unprotected EEPROM containing unique and very important calibration data. It was found that third party control software could and did corrupt the EEPROM data by accident and in an unpredictable fashion. ICOM never admitted any liability in the UK or USA and charged a hefty re-calibration fee. Their view was that the user shouldn't be messing with 3rd party software or the proprietary command set.
Drieg is probabably the only person who can help with a bricked Rigol and we are fortunate indeed that he wishes to use his time to help others.