Canon IPF8300 ink smudges / smears after print heads replaced.

Our Canon IPF8300 just got out of warranty and of course it had problem with the print heads. So we ordered pair of print heads to replace. After replacing print heads, we got another problem with the multi sensor. We have ordered a multi sensor and replaced it ourselves (service costs are ridiculous on out of warranty Canon product). We have followed all instructions for the replacement of the multi sensor. Before it couldn't find paper, after we replaced multi sensor, it can now find paper borders and load the paper.

The problem that we are experiencing right now is the ink smudges/smears on the paper.

Here what we have done to troubleshoot and eliminate the problem:

• Print head cleaning (A and B).
• Nozzle checks and cleaning.
• Print head adjustments.
• Increased gap between paper and the print head (from the paper menu).
• Tried to initiate optical axis adjustment, but failed, due to contamination on the paper.

It looks like both print heads dropping the ink. I'm not sure if both of them are faulty and what would be the chances of that. We have also printed out a PRINT INF and it looks like that both print heads have non-discharging nozzles. Could that be the cause of the problem? And what to do if it is?

So, right now we are kind of stuck and not sure what to do or to debug.
Could that be print heads?
Could that be PCB?
Could that be flexi cables?

Any help or suggestions are very much appreciated.

Thank you in advance,
P.S. I have attached pictures

 

May I ask where you obtained the procedure for changing the multisensor? It does not do a very good job in the manual. Thanks