TIU RS-232 Port?

Put it in a place that the connector is safe from abuse.

There should be two of these of the correct length on the port to secure the serial connector: 

You have the same problem on the Legacy base, same solution.

John,

there was 2 of those posts already on the TIU and the cable came with 2 of the same length.  Neither are quite long enough to hold it in place.  I may have some out in my computer bone yard so I'll take a look.  I may have to replace the screws instead of the posts.

Bob,

If the fit is real close, typically you can use a bit of force to get a turn or two of the screws into the posts. Also, loosen the posts a couple of turns where they screw into the TIU.

Also, loosen the posts a couple of turns where they screw into the TIU.

LOL, didn't even cross my mind

My TIU didn't have them, so I took some from my computer parts drawers, they worked fine and the connector fits and screws in.  Those nuts come in a number of lengths.

FIXED!!!

I found some posts, but most were just like what was on there.  I found 2 that were longer but the thread size was bigger.

I ended up taking the 2 that were on there off, putting a nut on them, then screwed them back in the TIU.  The nut brings the post out the thickness of the nut, making it possible to secure the plug.  Just backing the post out wasn't the answer as it was too loose to stay put.

That works. 

I was going to mention that when the post is unscrewed, it's next to impossible to connect to it without them coming loose or trying to screw themselves down.  I have a large assortment of them from my work in the distant past, so I had the size that fits and extends the length about 1/8", just the right amount.