Jamming at the horizontal transport unit exit

I am running up a new Bizhub C754e today with a FS-534 finisher and I am reminded of some problems with paper jams that I have had with this combination.
The first time we had trouble was with a customer who was an hour and a half drive away and was reporting "Jamming everywhere in the copier". Jamming everywhere usually means a jam in the finisher or towards the end of the paper path. Larger printers have multiple sheets of paper running through them at once to keep the time between prints as short as possible. A jam like this means that there is paper all through the machine when the jam occures and they all need to be removed before the machine will work again. This is described by normal people as jamming everywhere. In fact it is only jamming in the finisher.

I wasn't the first tech to have a look at the problem but the guy who was did a lot of testing but couldn't get it to jam. A couple of days later another call came in for the same problem so I went to have a look. All photocopiers keep a log of the latest jams including a code that describes where the jam occurred, the time, date and what paper was being used. When I looked at the log all I could see were document feeder jams. So I cleaned the ADF and replaced the feed rollers and then gave the machine a good test.

Since it was a decent drive to the office where the machine was located I really wanted to make sure that the problem was fixed but I had doubts. I was worried that we are missing something with jams not being logged so I turned on the option for the machine to display jam codes. Normally when there is a jam the machine will display a picture showing where paper needs to be removed from the machine but no information about what caused the jam. Now when there is a jam a code will be displayed on the screen. I asked the girl at reception if she could keep a manual log of any codes if the machine jams so we could have a better chance of fixing it.

Sure enough a couple of days later we got a call that the jamming had not stopped. I was surprised when I arrived that the receptionist had not only taken note of the lack of jam codes displayed but had used her phone to take pictures of the paper jammed in the machine before it was cleared. I was interested to see that not only wasn't the machine logging jam codes but won't display them either. The pictures though showed clearly that the front corner of the paper was catching at the finisher entrance. 

It didn't take too long after looking at the pictures that there was a groove cut into the plastic lower guide at the exit of the horizontal transport unit. 

The lower guide is removable (3 screws) and has a series of ridges that look like they are there to reduce the friction of the paper sliding over the plastic. However with the C754/FS-534 combo the edge of an A4 sheet lines up perfectly with the inside edge of the front most ridge. After a 200000 pages or so have gone through the paper actually cuts the plastic an causes a groove on the inside of this ridge. This causes the jamming.

To fix the problem we replaced this guide with a new one but that only fixed the problem for another 200000 pages and the jamming started again. So a final fix was to use a sharp knife to remove the bridge and then polish the plastic to smooth it out completely.

So the lesson here is to not always believe the logs.