LG fix hang on logo h815 with Octopus Box, thanks
 

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Opening "h815_v10b_00.oct"...OK
Setting options...OK
Reading partitions...OK
Formating USERDATA...OK
Formating ENCRYPT...OK
Writing PrimaryGPT...OK
Writing modem...OK
Writing pmic...OK
Writing sbl1...OK
Writing tz...OK
Writing sdi...OK
Writing hyp...OK
Writing rpm...OK
Writing aboot...OK
Writing sbl1bak...OK
Writing pmicbak...OK
Writing tzbak...OK
Writing hypbak...OK
Writing rpmbak...OK
Writing abootbak...OK
Writing sdibak...OK
Writing persist...OK
Writing sec...OK
Writing laf...OK
Writing boot...OK
Writing recovery...OK
Writing factory...OK
Writing raw_resources...
Writing raw_resourcesbak...
Writing system...OK
Writing cust...OK
Writing BackupGPT...OK
Reading partitions...OK
Formating RCT...OK
Formating MPT...OK
Finalizing...OK
Writing firmware done!
Performed by 2.6.0 Software version.

Thanks You also for good report. :)

lg h815 after flash set dead


Opening "H81520l_00_0124_Europe_United Kingdom.oct"...OK
Setting options...OK
Reading partitions...OK
Formating USERDATA...OK
Formating ENCRYPT...OK
Sending signature...OK
Writing PrimaryGPT...OK
Writing modem...OK
Writing pmic...OK
Writing sbl1...OK
Writing tz...OK
Writing sdi...OK
Writing hyp...OK
Writing rpm...OK
Writing aboot...OK
Writing sbl1bak...OK
Writing pmicbak...OK
Writing tzbak...OK
Writing hypbak...OK
Writing rpmbak...OK
Writing abootbak...OK
Writing sdibak...OK
Writing persist...OK
Writing sec...OK
Writing laf...OK
Writing boot...OK
Writing recovery...OK
Writing factory...OK
Writing raw_resources...OK
Writing raw_resourcesbak...OK
Writing system...OK
Writing cust...OK
Writing BackupGPT...OK
Reading partitions...OK
Formating RCT...OK
Formating MPT...OK
Finalizing...OK
Writing firmware done!
Performed by 2.7.3 Software version.

What was the problem with the phone? What was the firmware version in the phone before? Why You have decided to write firmware? Also post here full Software log, not reduced.