Not true - listen to Borygard.
The corrosion could have spread to the contacts of the wire harness and/or the IDC connections of the connector at the wire.
This screams corrosion related contact issues.... or bad IDC connections.
While in test; wiggle the wire harness at the connection(s) (at CPU board) to see if they flickering changes. Examine the contacts of the IDC connector to make sure they are clean and shiny.

since this seems to be related to a specific row; I'd be more inclined to believe this is a connector or a power issue to the row.

I would seriously consider verifying the harness assembly for that row.

So this was a bad cap on the powersupply on the Opto Board?
That's interesting... Good learning if true.

He showed during his video above that a whole row of optos was randomly flickering while in switch test.
While it's not conclusive proof yet; I suspect he's probably right as an unfiltered opto rail would appear to the cpu as pulsating like the video showed.
I'm sure he'll confirm it's fixed for sure once he has the machine back together.

The whole row seems to be blinking.
I'd check for bad connectors on the voltage going into the opto boards and/or a bad connector on the switch matrix for that row.
I don't have any experience with TZ; so you're on your own.