Remedy
Maximum unexpected flame losses exceeded.
Note: Combustion cover off can cause this.
Refer to the blocking error(s) that lead to this locking error. Check the fault history on appliance.
Possible incomplete purging of gas pipe.
Could also indicate a wide variety of issues such as undersized pipework or gas pressure dropping off, incorrectly routed condensate discharge, incorrectly sited flues, incorrectly wired etc.